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+{"metadata":{"orig_nbformat":4,"language_info":{"codemirror_mode":"text/x-c++src","file_extension":".cpp","mimetype":"text/x-c++src","name":"c++","version":"17"},"kernelspec":{"name":"xcpp17","display_name":"C++17","language":"C++17"}},"nbformat_minor":5,"nbformat":4,"cells":[{"cell_type":"markdown","source":"## Classes and Objects\n\nLet's try to implement our first class","metadata":{},"id":"e0e9c863-8720-40a4-a22c-00af773497fe"},{"cell_type":"code","source":"class aggregate {\n short s = 4;\n unsigned int i = 1u<<16;\n double x = 2.0;\n};","metadata":{"trusted":true},"execution_count":1,"outputs":[],"id":"bc685489-cf28-4a15-b0ee-fef2e6143f28"},{"cell_type":"code","source":"#include <iostream>\n\nint main() {\n aggregate agg;\n std::cout << \"s = \" << agg.s << std::endl;\n std::cout << \"i = \" << agg.i << std::endl;\n}","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stderr","text":"input_line_9:3:32: error: 's' is a private member of '__cling_N52::aggregate'\n std::cout << \"s = \" << agg.s << std::endl;\n ^\ninput_line_7:2:11: note: implicitly declared private here\n short s = 4;\n ^\ninput_line_9:4:32: error: 'i' is a private member of '__cling_N52::aggregate'\n std::cout << \"i = \" << agg.i << std::endl;\n ^\ninput_line_7:3:18: note: implicitly declared private here\n unsigned int i = 1u<<16;\n ^\n","output_type":"stream"},{"ename":"Interpreter Error","evalue":"","traceback":["Interpreter Error: "],"output_type":"error"}],"id":"4ada47eb-7158-4caf-aa60-0eb8df7e4769"},{"cell_type":"markdown","source":"That did not work. Why?","metadata":{},"id":"4035a6b6-f751-44fa-a579-a1166df4eed7"},{"cell_type":"markdown","source":"Because object-oriented programming is also about **encapsulation**. By making certain attributes (data members) and method (member functions) invisible to the outside, we\n - can enhance safety: better control over the state of an object\n - make sure that the internal implementation of the class can be changed without breaking outside code \n\nIn C++ we have three levels of access:\n - **public** = any one has access \n - **private** = only the class itself has access\n - **protected** = the class and its children have access\n \nThe difference between a struct and a class lies in their default setting\n\n| | class | struct |\n|:----------:|:-----:|:------:|\n| default is:|private| public |","metadata":{},"id":"159ef323-6f0a-49af-ac06-98804334e5d1"},{"cell_type":"code","source":"class aggregate {\n \n double x; // private by default\n \npublic:\n \n short s = 4;\n unsigned int i = 1u<<16;\n\n};\n\nstruct combo {\n \n int a; // public by default\n \nprivate:\n int internal; // not accessible from outside\n\n};","metadata":{"trusted":true},"execution_count":1,"outputs":[],"id":"7ea6dfba-43fe-4730-b845-4bd49c9b3e3a"},{"cell_type":"code","source":"#include <iostream>\n\nint main() {\n aggregate agg;\n std::cout << \"s = \" << agg.s << std::endl;\n std::cout << \"i = \" << agg.i << std::endl;\n\n combo s;\n s.a = 7;\n}\n\nmain();","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stdout","text":"s = 4\ni = 65536\n","output_type":"stream"}],"id":"6b4cd5c9-0ec3-451b-95b3-e9ad857eea83"},{"cell_type":"markdown","source":"An **object** is an instance of a class; different objects are different entities.","metadata":{},"id":"8c9241eb-1530-42db-8f50-542b8b74bbb8"},{"cell_type":"code","source":"int main() {\n \n aggregate a, b, c;\n \n a.s = 1;\n b.s = 2;\n c.s = 3;\n \n std::cout << \"a's short has a value of \" << a.s << '\\n'\n << \"b's short has a value of \" << b.s << '\\n'\n << \"c's short has a value of \" << c.s << std::endl;\n \n a = c;\n std::cout << \"now a.s = \" << a.s << std::endl;\n}","metadata":{"trusted":true},"execution_count":3,"outputs":[],"id":"2f93bb55-528a-4bac-8336-ccf98cc18af0"},{"cell_type":"code","source":"main();","metadata":{"trusted":true},"execution_count":4,"outputs":[{"name":"stdout","text":"a's short has a value of 1\nb's short has a value of 2\nc's short has a value of 3\nnow a.s = 3\n","output_type":"stream"}],"id":"e5ca8f44-4f3f-4142-8b5e-f5a3c31fee7e"},{"cell_type":"markdown","source":"### Constructors\n\n- Our class *aggregate* used *default member initializers* for setting initial values for its data members.\n- This is one possibility. The other is to use a *constructor* and a *member initializer list*.\n- Constructors are also required, if we want to run some start-up code as part of object creation.","metadata":{},"id":"fe29c0f5-6967-403d-b796-779fe1ccf4be"},{"cell_type":"code","source":"#include <iostream>\n\nclass myClass{\n \n public:\n myClass() : memb_(0) {\n std::cout << \"An instance of myClass was generated.\"\n << \" memb_ = \" << memb_ << std::endl;\n }\n \n private:\n int memb_; // some people adhere to the convention of marking data members by a trailing \"_\"\n}","metadata":{"trusted":true},"execution_count":6,"outputs":[],"id":"4c961b3c-ba83-46e6-aab1-08f1ad4102e3"},{"cell_type":"code","source":"int main() {\n myClass myObj;\n}\n\nmain();","metadata":{"trusted":true},"execution_count":7,"outputs":[{"name":"stdout","text":"An instance of myClass was generated. memb_ = 0\n","output_type":"stream"}],"id":"f501dce2-ef23-4345-8072-45ea85cb8c17"},{"cell_type":"markdown","source":"#### Multiple Constructors\nC++ allows to overload functions. One can use this to implement different constructors.","metadata":{},"id":"5a5ded92-91fc-4a2f-8628-d9531cd84ea2"},{"cell_type":"code","source":"class myClass{\n \n public:\n myClass() : memb_(0) {\n std::cout << \"An instance of myClass was generated.\"\n << \" memb_ = \" << memb_ << std::endl;\n }\n \n myClass( int member ) : memb_(member) {\n std::cout << \"An instance of myClass was generated.\"\n << \" memb_ = \" << memb_ << std::endl;\n }\n \n private:\n int memb_;\n}","metadata":{"trusted":true},"execution_count":8,"outputs":[],"id":"3f4cf1f6-8c50-4057-ab71-259c1046222a"},{"cell_type":"code","source":"int main() {\n myClass myObj1;\n myClass myObj2( 5 );\n}\n\nmain();","metadata":{"trusted":true},"execution_count":5,"outputs":[{"name":"stdout","text":"An instance of myClass was generated. memb_ = 0\nAn instance of myClass was generated. memb_ = 5\n","output_type":"stream"}],"id":"51015ed7-9f4e-40c0-bfa9-2b9f98cd0e1e"},{"cell_type":"markdown","source":"#### Constructor Delegation","metadata":{},"id":"ee95a999-1b5a-4c1b-b2a3-d7dc9a6b306f"},{"cell_type":"markdown","source":"In the example above the body of both constructors is identical. Such a code duplication is, of course, not nice and in violation of the **D**on't **R**epeat **Y**ourself principle. We can avoid this by using **constructor delegation**.","metadata":{},"id":"b977d057-634f-4027-a177-6866bf88160b"},{"cell_type":"code","source":"#include <iostream>\n\nclass myClass{\n \n public:\n myClass( int member ) : memb_(member) {\n std::cout << \"An instance of myClass was generated.\"\n << \" memb_ = \" << memb_ << std::endl;\n }\n\n myClass() : myClass(0) {}\n \n private:\n int memb_;\n};","metadata":{"trusted":true},"execution_count":4,"outputs":[],"id":"8eed6ec9-9ad6-48ab-b0e2-ab0ea35b9b57"},{"cell_type":"markdown","source":"#### Cleaning up: Destructors\nWhen an object goes out of scope and is destroyed we might want or need to do some housekeeping. For this we can implement a destructor.","metadata":{},"id":"fa5b47ea-8d12-4f55-8efe-c08588b81dbc"},{"cell_type":"code","source":"#include <iostream>\n\nclass VerboseClass{\n \n public:\n // c'tor\n VerboseClass() {\n std::cout << \"An instance of VerboseClass was generated.\" << std::endl;\n }\n\n // d'tor\n ~VerboseClass() {\n std::cout << \"An instance of VerboseClass was destroyed.\\n\" << std::endl;\n }\n};","metadata":{"trusted":true},"execution_count":7,"outputs":[],"id":"e456ce69-71e5-4169-b3e8-f302c3f72242"},{"cell_type":"code","source":"int main() {\n for( int k = 0; k < 3; k++ ) {\n VerboseClass talky;\n }\n}\n\nmain();","metadata":{"trusted":true},"execution_count":10,"outputs":[{"name":"stdout","text":"An instance of VerboseClass was generated.\nAn instance of VerboseClass was destroyed.\n\nAn instance of VerboseClass was generated.\nAn instance of VerboseClass was destroyed.\n\nAn instance of VerboseClass was generated.\nAn instance of VerboseClass was destroyed.\n\n","output_type":"stream"}],"id":"8fe56e9c-1842-4c29-84eb-1b20b3f7704a"},{"cell_type":"markdown","source":"#### Small Project: A Vector Class for Linear Algebra\nTasks:\n- We want to implement a class that represents a vector entity from linear algebra.\n- The size of the vector should be selectable at object creation -> need to allocate memory dynamically.\n- Access to vector entries should be 1-based -> operator overloading.\n- Implement simple methods, such as\n - scaling vector with a constant\n - adding two vectors together\n - compute the Euclidean inner product of two vectors","metadata":{},"id":"dffe4043-6959-4169-b0df-203a50d36e0f"},{"cell_type":"code","source":"// --------------------------------------\n// Start with the skeleton of the class\n// --------------------------------------\n\n#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n\n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n};","metadata":{"trusted":true},"execution_count":1,"outputs":[],"id":"f33e5eef-b396-4bfc-8031-f21b33839611"},{"cell_type":"code","source":"int main() {\n VectorClass myVec( 10 );\n}\n\nmain();","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stdout","text":"An instance of VectorClass was generated. dim_ = 10\n","output_type":"stream"}],"id":"af9910d6-a982-437d-9b55-1d0d01998f85"},{"cell_type":"markdown","source":"Our implementation is **missing an essential piece**? What could that be?","metadata":{},"id":"935b6f8d-d347-4edb-9807-f2ed3563dcaf"},{"cell_type":"code","source":"// --------------------------------------\n// Start with the skeleton of the class\n// --------------------------------------\n\n#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n};","metadata":{"trusted":true},"execution_count":6,"outputs":[],"id":"102897af-957e-43b7-a959-eb6ee468f35d"},{"cell_type":"code","source":"int main() {\n VectorClass myVec( 10 );\n}\n\nmain();","metadata":{"trusted":true},"execution_count":7,"outputs":[{"name":"stdout","text":"An instance of VectorClass was generated. dim_ = 10\nAn instance of VectorClass was destroyed and 80 bytes freed.\n","output_type":"stream"}],"id":"adcac578-0bca-4aed-8d13-4514826dd0e7"},{"cell_type":"markdown","source":"Our VectorClass is currently pretty useless, since we cannot manipulate the values of the vector entries. Making vec_ public would break encapsulation. Instead let's\n- overload the [] for providing one-based access\n- add a getter method for the dimension\n- add a member function to pretty-print the vector's entries","metadata":{},"id":"1a74105b-5453-49ab-aeed-e0371809fc52"},{"cell_type":"code","source":"#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ){\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n // pretty print vector to given output stream\n void print( std::ostream &os ) {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};","metadata":{"trusted":true},"execution_count":3,"outputs":[],"id":"a32eb08a-822a-4b83-b3d0-6de281acffba"},{"cell_type":"code","source":"// Let's test our extended class\n\nint main() {\n \n VectorClass myVec( 3 );\n \n myVec[ 1 ] = 3;\n myVec[ 2 ] = 2;\n myVec[ 3 ] = 1;\n \n myVec.print( std::cout );\n}\n\nmain();","metadata":{"trusted":true},"execution_count":4,"outputs":[{"name":"stdout","text":"An instance of VectorClass was generated. dim_ = 3\n(3, 2, 1)\nAn instance of VectorClass was destroyed and 24 bytes freed.\n","output_type":"stream"}],"id":"4eb50e73-21f5-4669-9464-32f11d958732"},{"cell_type":"markdown","source":"**What is left on our todo-list?**\nImplement simple methods, such as\n - scaling vector with a constant\n - adding two vectors together\n - compute the Euclidean inner product of two vectors","metadata":{},"id":"d8af8c97-2855-41f9-bda2-9d5ae341b7c0"},{"cell_type":"code","source":"%%file VectorClass.cpp\n\n#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ){\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n // pretty print vector to given output stream (default will be std::cout)\n void print( std::ostream &os = std::cout ) {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n // scale vector with a constant\n void scale( double factor ) {\n // leave that to students\n }\n \n // add to vectors together (that's actually a little bit tricky, due to the question \"where to put the result?\"\n // for the moment leave it with adding another vector to the one on which the method is called.\n \n // let us try the following, and determine, why it will fail ;-)\n void add( VectorClass other ) {\n\n // make sure that input vector has correct length\n assert( other.getDim() == dim_ );\n // for( unsigned int k = 0; k < dim_; k++ ) {\n // vec_[k] += other[k+1];\n // }\n for( unsigned int k = 1; k <= dim_; k++ ) {\n this->operator[](k) += other[k];\n }\n }\n \n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};\n\n// Modify driver a little bit\nint main() {\n\n const unsigned int dim = 10;\n \n // set up 1st vector\n VectorClass myVec( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n myVec[ idx ] = static_cast<double>( dim - idx + 1 );\n }\n myVec.print( std::cout );\n \n // set up 2nd vector\n VectorClass other( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n other[ idx ] = static_cast<double>( idx );\n }\n other.print( std::cout );\n \n // add the 2nd to the 1st\n myVec.add( other );\n myVec.print();\n}","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stdout","text":"Overwriting VectorClass.cpp\n","output_type":"stream"}],"id":"cdfde2f9-fafc-4a9f-99b7-4952720e4521"},{"cell_type":"code","source":"!g++ -g VectorClass.cpp","metadata":{"trusted":true},"execution_count":3,"outputs":[],"id":"f9331dc3-19ff-44a2-a8f5-6e258f9266d2"},{"cell_type":"code","source":"!./a.out","metadata":{"trusted":true},"execution_count":4,"outputs":[{"name":"stdout","text":"An instance of VectorClass was generated. dim_ = 10\n(10, 9, 8, 7, 6, 5, 4, 3, 2, 1)\nAn instance of VectorClass was generated. dim_ = 10\n(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\nAn instance of VectorClass was destroyed and 80 bytes freed.\n(11, 11, 11, 11, 11, 11, 11, 11, 11, 11)\nfree(): double free detected in tcache 2\nAborted\n","output_type":"stream"}],"id":"4f4d196d-761d-40e1-9d08-5df87307476b"},{"cell_type":"markdown","source":"**Note**: The adding itself seems to have worked correctly, but somehow we still have a problem. So what's wrong here?","metadata":{},"id":"3e04234e-4f33-44c4-9adb-0bde893019df"},{"cell_type":"markdown","source":"The answer to this is multifaceted:\n- Our implementation of *add()* used **call-by-copy**\n- Since we pass an object, its **copy constructor** is invoked\n- We haven't implemented one, but the compiler did automatically (thank's for that ;-)\n- Thus, the copy we get of **other** is a **flat** one!","metadata":{},"id":"7551ddc3-e449-47f1-bdc8-9a8080acdaf9"},{"cell_type":"markdown","source":"***\nWe can check on that by making the destructor tell us which block it is going to deallocate and run our code through valgrind:\n***\n**==> valgrind ./a.out**\n<div>\n==28488== Memcheck, a memory error detector</br>\n==28488== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.</br>\n==28488== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info</br>\n==28488== Command: ./a.out</br>\n==28488== </br>\nAn instance of VectorClass was generated. dim_ = 10</br>\n(10, 9, 8, 7, 6, 5, 4, 3, 2, 1)</br>\nAn instance of VectorClass was generated. dim_ = 10</br>\n(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)</br>\n<font color=\"red\">Going to delete memory starting at address 0x4d9b150</font></br>\nAn instance of VectorClass was destroyed and 80 bytes freed.</br>\n(11, 11, 11, 11, 11, 11, 11, 11, 11, 11)</br>\n<font color=\"red\">Going to delete memory starting at address 0x4d9b150</font></br>\n==28488== Invalid free() / delete / delete[] / realloc()</br>\n==28488== at 0x483758B: operator delete[](void*) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)</br>\n==28488== by 0x109500: VectorClass::~VectorClass() (VectorClass3.cpp:30)</br>\n==28488== by 0x109341: main (VectorClass3.cpp:93)</br>\n==28488== Address 0x4d9b150 is 0 bytes inside a block of size 80 free'd</br>\n==28488== at 0x483758B: operator delete[](void*) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)</br>\n==28488== by 0x109500: VectorClass::~VectorClass() (VectorClass3.cpp:30)</br>\n==28488== by 0x109322: main (VectorClass3.cpp:100)</br>\n==28488== Block was alloc'd at</br>\n==28488== at 0x483650F: operator new[](unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)</br>\n==28488== by 0x109450: VectorClass::VectorClass(unsigned int) (VectorClass3.cpp:15)</br>\n==28488== by 0x109291: main (VectorClass3.cpp:93)</br>\n==28488== </br>\nAn instance of VectorClass was destroyed and 80 bytes freed.</br>\nGoing to delete memory starting at address 0x4d9ac80</br>\nAn instance of VectorClass was destroyed and 80 bytes freed.</br>\n==28488== </br>\n==28488== HEAP SUMMARY:</br>\n==28488== in use at exit: 0 bytes in 0 blocks</br>\n==28488== total heap usage: 4 allocs, 5 frees, 73,888 bytes allocated</br>\n==28488== </br>\n==28488== All heap blocks were freed -- no leaks are possible</br>\n==28488== </br>\n==28488== For counts of detected and suppressed errors, rerun with: -v</br>\n==28488== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)</br>\n</div>","metadata":{},"id":"02714f7e-52c4-4890-8a87-05ca91d651e5"},{"cell_type":"markdown","source":"Another way to check on this is to remove the automatic copy constructor","metadata":{},"id":"48d75c49-dd79-420e-9e00-c75865245b5c"},{"cell_type":"code","source":"%%file VectorClass.cpp\n\n#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n\n // Don't allow the following default copy constructor either\n VectorClass( VectorClass &other ) = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ){\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n // pretty print vector to given output stream (default will be std::cout)\n void print( std::ostream &os = std::cout ) {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n // scale vector with a constant\n void scale( double factor ) {\n // leave that to students\n }\n \n // add to vectors together (that's actually a little bit tricky, due to the question \"where to put the result?\"\n // for the moment leave it with adding another vector to the one on which the method is called.\n \n // let us try the following, and determine, why it will fail ;-)\n void add( VectorClass other ) {\n\n // make sure that input vector has correct length\n assert( other.getDim() == dim_ );\n // for( unsigned int k = 0; k < dim_; k++ ) {\n // vec_[k] += other[k+1];\n // }\n for( unsigned int k = 1; k <= dim_; k++ ) {\n this->operator[](k) += other[k];\n }\n }\n \n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};\n\n// Modify driver a little bit\nint main() {\n\n const unsigned int dim = 10;\n \n // set up 1st vector\n VectorClass myVec( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n myVec[ idx ] = static_cast<double>( dim - idx + 1 );\n }\n myVec.print( std::cout );\n \n // set up 2nd vector\n VectorClass other( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n other[ idx ] = static_cast<double>( idx );\n }\n other.print( std::cout );\n \n // add the 2nd to the 1st\n myVec.add( other );\n myVec.print();\n}","metadata":{"trusted":true},"execution_count":1,"outputs":[{"name":"stdout","text":"Overwriting VectorClass.cpp\n","output_type":"stream"}],"id":"def80c0f-89b6-4e00-995a-14b8e800975c"},{"cell_type":"code","source":"!g++ VectorClass.cpp","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stdout","text":"VectorClass.cpp: In function ‘int main()’:\nVectorClass.cpp:101:22: error: use of deleted function ‘VectorClass::VectorClass(VectorClass&)’\n myVec.add( other );\n ^\nVectorClass.cpp:26:9: note: declared here\n VectorClass( VectorClass &other ) = delete;\n ^~~~~~~~~~~\nVectorClass.cpp:63:14: note: initializing argument 1 of ‘void VectorClass::add(VectorClass)’\n void add( VectorClass other ) {\n ^~~\n","output_type":"stream"}],"id":"473de9eb-b04c-4087-8444-8d4b3c4c9fb8"},{"cell_type":"markdown","source":"#### Solution?\nHow should we resolve the issue?\n***\nFor the current case the best solution is to change the interface of our `add()` method to be\n\n`void add( const VectorClass& other )`\n\nThe `const` is no must, but makes it clear to other programmers and the compiler that we are not going to change the object\nother inside add().","metadata":{},"id":"91724843-2e97-4862-888a-291fda71444a"},{"cell_type":"code","source":"#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n\n // Don't allow the following default copy constructor either\n VectorClass( VectorClass &other ) = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ){\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n // pretty print vector to given output stream (default will be std::cout)\n void print( std::ostream &os = std::cout ) {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n // scale vector with a constant\n void scale( double factor ) {\n // leave that to students\n }\n \n // add to vectors together (that's actually a little bit tricky, due to the question \"where to put the result?\"\n // for the moment leave it with adding another vector to the one on which the method is called.\n \n // let us try the following, and determine, why it will fail ;-)\n void add( const VectorClass& other ) {\n\n // make sure that input vector has correct length\n assert( other.getDim() == dim_ );\n // for( unsigned int k = 0; k < dim_; k++ ) {\n // vec_[k] += other[k+1];\n // }\n for( unsigned int k = 1; k <= dim_; k++ ) {\n this->operator[](k) += other[k];\n }\n }\n \n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};\n\n// Modify driver a little bit\nint main() {\n\n const unsigned int dim = 10;\n \n // set up 1st vector\n VectorClass myVec( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n myVec[ idx ] = static_cast<double>( dim - idx + 1 );\n }\n myVec.print( std::cout );\n \n // set up 2nd vector\n VectorClass other( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n other[ idx ] = static_cast<double>( idx );\n }\n other.print( std::cout );\n \n // add the 2nd to the 1st\n myVec.add( other );\n myVec.print();\n}","metadata":{"trusted":true},"execution_count":4,"outputs":[{"name":"stderr","text":"input_line_9:61:45: error: no viable overloaded operator[] for type 'const VectorClass'\n this->operator[](k) += other[k];\n ~~~~~^~\ninput_line_9:32:17: note: candidate function not viable: 'this' argument has type 'const VectorClass', but method is not marked const\n double& operator[] ( unsigned int index ){\n ^\ninput_line_9:71:13: error: function definition is not allowed here\n int main() {\n ^\n","output_type":"stream"},{"ename":"Interpreter Error","evalue":"","traceback":["Interpreter Error: "],"output_type":"error"}],"id":"30eccd22-8c5e-4062-a1d1-8006981aae99"},{"cell_type":"markdown","source":"***\nAh, okay. So the `const` was a good idea, but requires a little bit of extra work!\n\nWe need to implement a second version of the operator overloading that returns a const reference!","metadata":{},"id":"a6bfec6d-9eba-4e34-9ec8-e74bfa485664"},{"cell_type":"code","source":"#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \n public:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n }\n\n // Don't allow the default constructor [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n\n // Don't allow the following default copy constructor either\n VectorClass( VectorClass &other ) = delete;\n \n // We need to implement a destructor to free the dynamic memory again, otherwise we easily produce\n // memory leaks\n ~VectorClass() {\n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ){\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n \n // overload the [] for accessing individual entries\n const double& operator[] ( unsigned int index ) {\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n \n // pretty print vector to given output stream (default will be std::cout)\n void print( std::ostream &os = std::cout ) {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n // scale vector with a constant\n void scale( double factor ) {\n // leave that to students\n }\n \n // add to vectors together (that's actually a little bit tricky, due to the question \"where to put the result?\"\n // for the moment leave it with adding another vector to the one on which the method is called.\n \n // let us try the following, and determine, why it will fail ;-)\n void add( const VectorClass& other ) {\n\n // make sure that input vector has correct length\n assert( other.getDim() == dim_ );\n // for( unsigned int k = 0; k < dim_; k++ ) {\n // vec_[k] += other[k+1];\n // }\n for( unsigned int k = 1; k <= dim_; k++ ) {\n this->operator[](k) += other[k];\n }\n }\n \n private:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};\n\n// Modify driver a little bit\nint main() {\n\n const unsigned int dim = 10;\n \n // set up 1st vector\n VectorClass myVec( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n myVec[ idx ] = static_cast<double>( dim - idx + 1 );\n }\n myVec.print( std::cout );\n \n // set up 2nd vector\n VectorClass other( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n other[ idx ] = static_cast<double>( idx );\n }\n other.print( std::cout );\n \n // add the 2nd to the 1st\n myVec.add( other );\n myVec.print();\n}","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stderr","text":"input_line_10:38:23: error: functions that differ only in their return type cannot be overloaded\n const double& operator[] ( unsigned int index ) {\n ~~~~~~~ ^\ninput_line_10:32:17: note: previous definition is here\n double& operator[] ( unsigned int index ){\n ~~~~~~~ ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[50], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:14:23: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [50]]\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, const unsigned int &, void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:14:78: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = unsigned int]\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n ^\ninput_line_10:14:78: error: use of overloaded operator '<<' is ambiguous (with operand types 'basic_ostream<char, std::char_traits<char> >' and 'unsigned int')\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[46], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:25:23: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [46]]\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n ^\ninput_line_10:25:74: error: use of overloaded operator '<<' is ambiguous (with operand types 'basic_ostream<char, std::char_traits<char> >' and 'unsigned long')\n std::cout << \"An instance of VectorClass was destroyed and \" << dim_ * sizeof(double)\n ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[2], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:45:16: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [2]]\n os << \"(\";\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, const double &, void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:47:20: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = double]\n os << vec_[k] << \", \";\n ^\ninput_line_10:47:20: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'double')\n os << vec_[k] << \", \";\n ~~ ^ ~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\ninput_line_10:49:16: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'double')\n os << vec_[dim_-1] << \")\" << std::endl;\n ~~ ^ ~~~~~~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\ninput_line_10:68:45: error: no viable overloaded operator[] for type 'const VectorClass'\n this->operator[](k) += other[k];\n ~~~~~^~\ninput_line_10:32:17: note: candidate function not viable: 'this' argument has type 'const VectorClass', but method is not marked const\n double& operator[] ( unsigned int index ){\n ^\ninput_line_10:78:13: error: function definition is not allowed here\n int main() {\n ^\nIn file included from input_line_5:1:\nIn file included from /srv/conda/envs/notebook/include/xeus/xinterpreter.hpp:17:\nIn file included from /srv/conda/envs/notebook/include/xeus/xcomm.hpp:19:\nIn file included from /srv/conda/envs/notebook/include/nlohmann/json.hpp:42:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/iterator:64:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:568:8: error: no member named 'setstate' in 'std::basic_ostream<char>'\n __out.setstate(ios_base::badbit);\n ~~~~~ ^\ninput_line_10:14:23: note: in instantiation of function template specialization 'std::operator<<<std::char_traits<char> >' requested here\n std::cout << \"An instance of VectorClass was generated. dim_ = \" << dim_ << std::endl;\n ^\n","output_type":"stream"},{"ename":"Interpreter Error","evalue":"","traceback":["Interpreter Error: "],"output_type":"error"}],"id":"15b02a70-a496-4098-a446-9a60ee30b116"},{"cell_type":"markdown","source":"Shoot, we have a problem with the **signature** now!\n\nBut, fortunately, there is a way out of this:\n- We can tell the compiler that a member function does not alter its object! This will also be part of the signature. So we can implement our overloading as\n`const double& operator[] ( unsigned int index ) const`\n- We might want to do this also for any other member function that does not change the object, like e.g. `print()`\n\nIf we do this, we end up with the final version:","metadata":{},"id":"6a78d290-77dc-43a5-93f5-15fa2c650ddb"},{"cell_type":"code","source":"#include <iostream>\n#include <cassert>\n\nclass VectorClass{\n \npublic:\n \n // User should specify dimension at object creation\n VectorClass( unsigned int dim ) : dim_(dim) {\n \n // don't allow vectors with zero dimension\n assert( dim_ > 0 );\n\n // allocate memory (will throw an exception, if it fails)\n vec_ = new double[ dim_ ];\n \n // be talkative ;-)\n std::cout << \"An instance of VectorClass was generated. dim_ = \" \n << dim_ << std::endl;\n }\n\n // Don't allow the default constructor\n // [prior to C++11 you would solve this by making it private]\n VectorClass() = delete;\n\n // Don't allow the following default copy constructor either \n VectorClass( VectorClass &other ) = delete;\n \n // We need to implement a destructor to free the dynamic memory again,\n // otherwise we easily produce memory leaks\n ~VectorClass() {\n std::cout << \"Going to delete memory starting at address \"\n << vec_ << std::endl;\n \n delete[] vec_;\n std::cout << \"An instance of VectorClass was destroyed and \"\n << dim_ * sizeof(double)\n << \" bytes freed.\" << std::endl;\n }\n\n // provide access to the vector's dimension\n unsigned int getDim() const { return dim_; }\n \n // overload the [] for accessing individual entries\n double& operator[] ( unsigned int index ) {\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n const double& operator[] ( unsigned int index ) const {\n assert( index != 0 && index <= dim_ );\n return vec_[index-1];\n }\n\n // pretty print vector to given output stream (default will be std::cout)\n void print( std::ostream &os = std::cout ) const {\n os << \"(\";\n for( unsigned int k = 0; k < dim_-1; k++ ) {\n os << vec_[k] << \", \";\n }\n os << vec_[dim_-1] << \")\" << std::endl;\n }\n \n // scale vector with a constant\n void scale( double factor ) {\n // leave that to students\n }\n \n // add to vectors together (that's actually a little bit tricky,\n // due to the question \"where to put the result?\"\n // for the moment leave it with adding another vector to the one on which\n // the method is called.\n void add( const VectorClass& other ) {\n\n // make sure that input vector has correct length\n assert( other.getDim() == dim_ );\n // for( unsigned int k = 0; k < dim_; k++ ) {\n // vec_[k] += other[k+1];\n // }\n for( unsigned int k = 1; k <= dim_; k++ ) {\n this->operator[](k) += other[k];\n }\n }\n \nprivate:\n unsigned int dim_; // dimension of vector\n double* vec_; // entries of vector\n\n};\n\n// Modify driver a little bit\nint main() {\n\n const unsigned int dim = 10;\n \n // set up 1st vector\n VectorClass myVec( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n myVec[ idx ] = static_cast<double>( dim - idx + 1 );\n }\n myVec.print( std::cout );\n \n // set up 2nd vector\n VectorClass other( dim );\n for( unsigned int idx = 1; idx <= dim; idx ++ ) {\n other[ idx ] = static_cast<double>( idx );\n }\n other.print( std::cout );\n \n // add the 2nd to the 1st\n myVec.add( other );\n myVec.print();\n}","metadata":{"trusted":true},"execution_count":2,"outputs":[{"name":"stderr","text":"In file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[50], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:14:15: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [50]]\n std::cout << \"An instance of VectorClass was generated. dim_ = \" \n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, const unsigned int &, void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:15:15: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = unsigned int]\n << dim_ << std::endl;\n ^\ninput_line_10:15:15: error: use of overloaded operator '<<' is ambiguous (with operand types 'basic_ostream<char, std::char_traits<char> >' and 'unsigned int')\n << dim_ << std::endl;\n ^ ~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[44], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:26:15: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [44]]\n std::cout << \"Going to delete memory starting at address \"\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, double *const &, void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:27:15: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = double *]\n << vec_ << std::endl;\n ^\ninput_line_10:27:26: error: reference to overloaded function could not be resolved; did you mean to call it?\n << vec_ << std::endl;\n ^~~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:599:5: note: possible target for call\n endl(basic_ostream<_CharT, _Traits>& __os)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/string_view:580:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>] not viable: no overload of 'endl' matching 'basic_string_view<char, std::char_traits<char> >' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __os,\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/system_error:217:5: note: candidate function not viable: no overload of 'endl' matching 'const std::error_code' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:117:7: note: candidate function not viable: no overload of 'endl' matching 'std::basic_ostream<char, std::char_traits<char> >::__ios_type &(*)(std::basic_ostream<char, std::char_traits<char> >::__ios_type &)' (aka 'basic_ios<char, std::char_traits<char> > &(*)(basic_ios<char, std::char_traits<char> > &)') for 1st argument\n operator<<(__ios_type& (*__pf)(__ios_type&))\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:127:7: note: candidate function not viable: no overload of 'endl' matching 'std::ios_base &(*)(std::ios_base &)' for 1st argument\n operator<<(ios_base& (*__pf) (ios_base&))\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function not viable: no overload of 'endl' matching 'long' for 1st argument\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function not viable: no overload of 'endl' matching 'bool' for 1st argument\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function not viable: no overload of 'endl' matching 'short' for 1st argument\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function not viable: no overload of 'endl' matching 'unsigned short' for 1st argument\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function not viable: no overload of 'endl' matching 'int' for 1st argument\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function not viable: no overload of 'endl' matching 'long long' for 1st argument\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function not viable: no overload of 'endl' matching 'unsigned long long' for 1st argument\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function not viable: no overload of 'endl' matching 'float' for 1st argument\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function not viable: no overload of 'endl' matching 'long double' for 1st argument\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:250:7: note: candidate function not viable: no overload of 'endl' matching 'std::nullptr_t' (aka 'nullptr_t') for 1st argument\n operator<<(nullptr_t)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:276:7: note: candidate function not viable: no overload of 'endl' matching 'std::basic_ostream<char, std::char_traits<char> >::__streambuf_type *' (aka 'basic_streambuf<char, std::char_traits<char> > *') for 1st argument\n operator<<(__streambuf_type* __sb);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:506:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>] not viable: no overload of 'endl' matching 'char' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function not viable: no overload of 'endl' matching 'char' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function not viable: no overload of 'endl' matching 'char' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function not viable: no overload of 'endl' matching 'signed char' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function not viable: no overload of 'endl' matching 'unsigned char' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:548:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>] not viable: no overload of 'endl' matching 'const char *' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:565:5: note: candidate function not viable: no overload of 'endl' matching 'const char *' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, const char* __s)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:578:5: note: candidate function not viable: no overload of 'endl' matching 'const signed char *' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:583:5: note: candidate function not viable: no overload of 'endl' matching 'const unsigned char *' for 2nd argument\n operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/ostream.tcc:321:5: note: candidate function not viable: no overload of 'endl' matching 'const char *' for 2nd argument\n operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/basic_string.h:6419:5: note: candidate template ignored: couldn't infer template argument '_Alloc'\n operator<<(basic_ostream<_CharT, _Traits>& __os,\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/cstddef:130:5: note: candidate template ignored: couldn't infer template argument '_IntegerType'\n operator<<(byte __b, _IntegerType __shift) noexcept\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:691:5: note: candidate template ignored: couldn't infer template argument '_Tp'\n operator<<(_Ostream&& __os, const _Tp& __x)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/shared_ptr.h:66:5: note: candidate template ignored: couldn't infer template argument '_Tp'\n operator<<(std::basic_ostream<_Ch, _Tr>& __os,\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:413:5: note: candidate template ignored: couldn't infer template argument '_Dom'\n _DEFINE_EXPR_BINARY_OPERATOR(<<, __shift_left)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:370:5: note: expanded from macro '_DEFINE_EXPR_BINARY_OPERATOR'\n operator _Op(const typename _Dom::value_type& __t, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:413:5: note: candidate template ignored: couldn't infer template argument '_Dom'\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:396:5: note: expanded from macro '_DEFINE_EXPR_BINARY_OPERATOR'\n operator _Op(const valarray<typename _Dom::value_type>& __v, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1193:1: note: candidate template ignored: couldn't infer template argument '_Tp'\n_DEFINE_BINARY_OPERATOR(<<, __shift_left)\n^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1177:5: note: expanded from macro '_DEFINE_BINARY_OPERATOR'\n operator _Op(const typename valarray<_Tp>::value_type& __t, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:413:5: note: candidate template ignored: could not match '_Expr' against 'basic_ostream'\n _DEFINE_EXPR_BINARY_OPERATOR(<<, __shift_left)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:344:5: note: expanded from macro '_DEFINE_EXPR_BINARY_OPERATOR'\n operator _Op(const _Expr<_Dom1, typename _Dom1::value_type>& __v, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:413:5: note: candidate template ignored: could not match '_Expr' against 'basic_ostream'\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:357:5: note: expanded from macro '_DEFINE_EXPR_BINARY_OPERATOR'\n operator _Op(const _Expr<_Dom, typename _Dom::value_type>& __v, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:413:5: note: candidate template ignored: could not match '_Expr' against 'basic_ostream'\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/valarray_after.h:383:5: note: expanded from macro '_DEFINE_EXPR_BINARY_OPERATOR'\n operator _Op(const _Expr<_Dom,typename _Dom::value_type>& __e, \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1193:1: note: candidate template ignored: could not match 'valarray' against 'basic_ostream'\n_DEFINE_BINARY_OPERATOR(<<, __shift_left)\n^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1155:5: note: expanded from macro '_DEFINE_BINARY_OPERATOR'\n operator _Op(const valarray<_Tp>& __v, const valarray<_Tp>& __w) \\\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1193:1: note: candidate template ignored: could not match 'valarray' against 'basic_ostream'\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/valarray:1166:5: note: expanded from macro '_DEFINE_BINARY_OPERATOR'\n operator _Op(const valarray<_Tp>& __v, \\\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[46], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:30:15: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [46]]\n std::cout << \"An instance of VectorClass was destroyed and \"\n ^\ninput_line_10:31:15: error: use of overloaded operator '<<' is ambiguous (with operand types 'basic_ostream<char, std::char_traits<char> >' and 'unsigned long')\n << dim_ * sizeof(double)\n ^ ~~~~~~~~~~~~~~~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, char const (&)[2], void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:48:8: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = char [2]]\n os << \"(\";\n ^\nIn file included from input_line_1:1:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/new:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/exception:144:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/nested_exception.h:40:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/bits/move.h:55:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/type_traits:137:31: error: no member named 'value' in 'std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >'\n : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type\n ~~~~~^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:685:24: note: in instantiation of template class 'std::__and_<std::__not_<std::is_lvalue_reference<std::basic_ostream<char> &> >, std::__is_convertible_to_basic_ostream<std::basic_ostream<char> &>, std::__is_insertable<std::basic_ostream<char> &, const double &, void> >' requested here\n typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,\n ^\ninput_line_10:50:10: note: while substituting deduced template arguments into function template 'operator<<' [with _Ostream = std::basic_ostream<char> &, _Tp = double]\n os << vec_[k] << \", \";\n ^\ninput_line_10:50:10: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'double')\n os << vec_[k] << \", \";\n ~~ ^ ~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\ninput_line_10:52:8: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'double')\n os << vec_[dim_-1] << \")\" << std::endl;\n ~~ ^ ~~~~~~~~~~~~\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:166:7: note: candidate function\n operator<<(long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:174:7: note: candidate function\n operator<<(bool __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:178:7: note: candidate function\n operator<<(short __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:181:7: note: candidate function\n operator<<(unsigned short __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:189:7: note: candidate function\n operator<<(int __n);\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:201:7: note: candidate function\n operator<<(long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:205:7: note: candidate function\n operator<<(unsigned long long __n)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:224:7: note: candidate function\n operator<<(float __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:232:7: note: candidate function\n operator<<(long double __f)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:517:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:511:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>]\n operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:523:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, signed char __c)\n ^\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:528:5: note: candidate function [with _Traits = std::char_traits<char>]\n operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)\n ^\ninput_line_10:81:13: error: function definition is not allowed here\n int main() {\n ^\nIn file included from input_line_5:1:\nIn file included from /srv/conda/envs/notebook/include/xeus/xinterpreter.hpp:17:\nIn file included from /srv/conda/envs/notebook/include/xeus/xcomm.hpp:19:\nIn file included from /srv/conda/envs/notebook/include/nlohmann/json.hpp:42:\nIn file included from /srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/iterator:64:\n/srv/conda/envs/notebook/bin/../lib/gcc/../../x86_64-conda-linux-gnu/include/c++/9.4.0/ostream:568:8: error: no member named 'setstate' in 'std::basic_ostream<char>'\n __out.setstate(ios_base::badbit);\n ~~~~~ ^\ninput_line_10:14:15: note: in instantiation of function template specialization 'std::operator<<<std::char_traits<char> >' requested here\n std::cout << \"An instance of VectorClass was generated. dim_ = \" \n ^\n","output_type":"stream"},{"ename":"Interpreter Error","evalue":"","traceback":["Interpreter Error: "],"output_type":"error"}],"id":"0b2a852d-2a07-4f2a-85d2-7833051474d7"},{"cell_type":"code","source":"","metadata":{},"execution_count":null,"outputs":[],"id":"794e3f92-27e2-4362-89d9-d293b6463ee6"}]}
\ No newline at end of file