Add CudaBackend, CudaSympyPrinter

Add CudaBackend, CudaSympyPrinter to extract CUDA-specific code from CBackend, CustomSympyPrinter

Cuda built-ins are added to CudaSympyPrinter.known_functions to use them as sympy.Function

pystencils/display_utils.py

-import sympy as sp
 from typing import Any, Dict, Optional
+
+import sympy as sp
+
 from pystencils.astnodes import KernelFunction
 
 
@@ -32,7 +34,7 @@ def highlight_cpp(code: str):
     return HTML(highlight(code, CppLexer(), HtmlFormatter()))
 
 
-def show_code(ast: KernelFunction):
+def show_code(ast: KernelFunction, custom_backend=None):
     """Returns an object to display generated code (C/C++ or CUDA)
 
     Can either  be displayed as HTML in Jupyter notebooks or printed as normal string.
@@ -45,11 +47,11 @@ def show_code(ast: KernelFunction):
             self.ast = ast_input
 
         def _repr_html_(self):
-            return highlight_cpp(generate_c(self.ast, dialect=dialect)).__html__()
+            return highlight_cpp(generate_c(self.ast, dialect=dialect, custom_backend=custom_backend)).__html__()
 
         def __str__(self):
-            return generate_c(self.ast, dialect=dialect)
+            return generate_c(self.ast, dialect=dialect, custom_backend=custom_backend)
 
         def __repr__(self):
-            return generate_c(self.ast, dialect=dialect)
+            return generate_c(self.ast, dialect=dialect, custom_backend=custom_backend)
     return CodeDisplay(ast)