Fix #10: Avoid jinja2 dependency

This commit avoid dependency of core pystencils on jinja2.
However this could make the printing of some AST-nodes less elegant.

pystencils/astnodes.py

 import uuid
 from typing import Any, List, Optional, Sequence, Set, Union
 
-import jinja2
 import sympy as sp
 
 from pystencils.data_types import TypedSymbol, cast_func, create_type
@@ -673,7 +672,7 @@ class DestructuringBindingsForFieldClass(Node):
         FieldShapeSymbol: "shape[%i]",
         FieldStrideSymbol: "stride[%i]"
     }
-    CLASS_NAME_TEMPLATE = jinja2.Template("PyStencilsField<{{ dtype }}, {{ ndim }}>")
+    CLASS_NAME_TEMPLATE = "PyStencilsField<{dtype}, {ndim}>"
 
     @property
     def fields_accessed(self) -> Set['ResolvedFieldAccess']:
@@ -703,7 +702,7 @@ class DestructuringBindingsForFieldClass(Node):
         undefined_field_symbols = self.symbols_defined
         corresponding_field_names = {s.field_name for s in undefined_field_symbols if hasattr(s, 'field_name')}
         corresponding_field_names |= {s.field_names[0] for s in undefined_field_symbols if hasattr(s, 'field_names')}
-        return {TypedSymbol(f, self.CLASS_NAME_TEMPLATE.render(dtype=field_map[f].dtype, ndim=field_map[f].ndim) + '&')
+        return {TypedSymbol(f, self.CLASS_NAME_TEMPLATE.format(dtype=field_map[f].dtype, ndim=field_map[f].ndim) + '&')
                 for f in corresponding_field_names} | \
             (self.body.undefined_symbols - undefined_field_symbols)
 

pystencils/backends/cbackend.py

 from collections import namedtuple
 from typing import Set
 
-import jinja2
 import sympy as sp
 from sympy.core import S
 from sympy.printing.ccode import C89CodePrinter
@@ -9,11 +8,12 @@ from sympy.printing.ccode import C89CodePrinter
 from pystencils.astnodes import KernelFunction, Node
 from pystencils.cpu.vectorization import vec_all, vec_any
 from pystencils.data_types import (
-    PointerType, VectorType, address_of, cast_func, create_type, get_type_of_expression, reinterpret_cast_func,
-    vector_memory_access)
+    PointerType, VectorType, address_of, cast_func, create_type, get_type_of_expression,
+    reinterpret_cast_func, vector_memory_access)
 from pystencils.fast_approximation import fast_division, fast_inv_sqrt, fast_sqrt
 from pystencils.integer_functions import (
-    bit_shift_left, bit_shift_right, bitwise_and, bitwise_or, bitwise_xor, int_div, int_power_of_2, modulo_ceil)
+    bit_shift_left, bit_shift_right, bitwise_and, bitwise_or, bitwise_xor,
+    int_div, int_power_of_2, modulo_ceil)
 from pystencils.kernelparameters import FieldPointerSymbol
 
 try:
@@ -271,18 +271,11 @@ class CBackend:
                                   for u in undefined_field_symbols
                                   ]
         destructuring_bindings.sort()  # only for code aesthetics
-        template = jinja2.Template(
-            """{
-   {% for binding in bindings -%}
-   {{ binding | indent(3) }}
-   {% endfor -%}
-   {{ block | indent(3) }}
-}
-
-""")
-        code = template.render(bindings=destructuring_bindings,
-                               block=self._print(node.body))
-        return code
+        return "{\n" + self._indent + \
+            ("\n" + self._indent).join(destructuring_bindings) + \
+            "\n" + self._indent + \
+            ("\n" + self._indent).join(self._print(node.body).splitlines()) + \
+            "\n}"
 
 
 # ------------------------------------------ Helper function & classes -------------------------------------------------

pystencils_tests/test_destructuring_field_class.py

 import sympy
-import jinja2
-
 
 import pystencils
 from pystencils.astnodes import DestructuringBindingsForFieldClass
-from pystencils.kernelparameters import  FieldPointerSymbol, FieldShapeSymbol, FieldStrideSymbol
-
+from pystencils.kernelparameters import FieldPointerSymbol, FieldShapeSymbol, FieldStrideSymbol
 
 
 def test_destructuring_field_class():
@@ -28,12 +25,13 @@ class DestructuringEmojiClass(DestructuringBindingsForFieldClass):
         FieldShapeSymbol: "😳_%i",
         FieldStrideSymbol: "🥵_%i"
     }
-    CLASS_NAME_TEMPLATE = jinja2.Template("🤯<{{ dtype }}, {{ ndim }}>")
+    CLASS_NAME_TEMPLATE = "🤯<{dtype}, {ndim}>"
+
     def __init__(self, node):
         super().__init__(node)
         self.headers = []
-        
-    
+
+
 def test_destructuring_alternative_field_class():
     z, x, y = pystencils.fields("z, y, x: [2d]")
 
@@ -44,6 +42,7 @@ def test_destructuring_alternative_field_class():
     ast.body = DestructuringEmojiClass(ast.body)
     print(pystencils.show_code(ast))
 
+
 def main():
     test_destructuring_field_class()
     test_destructuring_alternative_field_class()