improved print_constant (pyccel#1120)

Print unknown constants using their values. This fixes pyccel#1047 but may be
reverted in pyccel#1811 to prefer declaring constants with names. However this
PR also adds support for `NaN` in C and an associated test. It also
removes the duplicate `_print_Constant` function.

---------

Co-authored-by: EmilyBourne <louise.bourne@gmail.com>

Author: bauom

CHANGELOG.md

@@ -33,6 +33,9 @@ All notable changes to this project will be documented in this file.
 -   #1785 : Add missing cast when creating an array of booleans from non-boolean values.
 -   #1821 : Ensure an error is raised when creating an ambiguous interface.
 -   #1842 : Fix homogeneous tuples incorrectly identified as inhomogeneous.
+-   #1853 : Fix translation of a file whose name conflicts with Fortran keywords.
+-   Link and mention `devel` branch, not `master`.
+-   #1047 : Print the value of an unrecognised constant.
 
 ### Changed
 

pyccel/codegen/printing/ccode.py

@@ -9,7 +9,7 @@
 
 from pyccel.ast.basic     import ScopedAstNode
 
-from pyccel.ast.builtins  import PythonRange, PythonComplex
+from pyccel.ast.builtins  import PythonRange, PythonComplex, DtypePrecisionToCastFunction
 from pyccel.ast.builtins  import PythonPrint, PythonType
 from pyccel.ast.builtins  import PythonList, PythonTuple
 
@@ -1963,28 +1963,6 @@ def _print_FunctionCall(self, expr):
         else:
             return call_code
 
-    def _print_Constant(self, expr):
-        """ Convert a Python expression with a math constant call to C
-        function call
-
-        Parameters
-        ----------
-            expr : Pyccel ast node
-                Python expression with a Math constant
-
-        Returns
-        -------
-            string
-                String represent the value of the constant
-
-        Example
-        -------
-            math.pi ==> 3.14159265358979
-
-        """
-        val = LiteralFloat(expr.value)
-        return self._print(val)
-
     def _print_Return(self, expr):
         code = ''
         args = [ObjectAddress(a) if isinstance(a, Variable) and self.is_c_pointer(a) else a for a in expr.expr]
@@ -2329,14 +2307,19 @@ def _print_Constant(self, expr):
         if expr == math_constants['inf']:
             self.add_import(c_imports['math'])
             return 'HUGE_VAL'
+        elif expr == math_constants['nan']:
+            self.add_import(c_imports['math'])
+            return 'NAN'
         elif expr == math_constants['pi']:
             self.add_import(c_imports['math'])
             return 'M_PI'
         elif expr == math_constants['e']:
             self.add_import(c_imports['math'])
             return 'M_E'
         else:
-            raise NotImplementedError("Constant not implemented")
+            cast_func = DtypePrecisionToCastFunction[expr.dtype]
+            return self._print(cast_func(expr.value))
+
 
     def _print_Variable(self, expr):
         if self.is_c_pointer(expr):

pyccel/codegen/printing/fcode.py

@@ -963,6 +963,9 @@ def _print_FunctionCallArgument(self, expr):
             return '{}'.format(self._print(expr.value))
 
     def _print_Constant(self, expr):
+        if expr == math_constants['nan']:
+            errors.report("Can't print nan in Fortran",
+                    severity='error', symbol=expr)
         val = LiteralFloat(expr.value)
         return self._print(val)
 

tests/pyccel/scripts/print_nan.py

@@ -0,0 +1,6 @@
+# pylint: disable=missing-function-docstring, missing-module-docstring
+from math import nan
+
+if __name__ == '__main__':
+    print(nan)
+

tests/pyccel/test_pyccel.py

@@ -733,6 +733,19 @@ def test_print_strings(language):
     types = str
     pyccel_test("scripts/print_strings.py", language=language, output_dtype=types)
 
+#------------------------------------------------------------------------------
+@pytest.mark.parametrize( 'language', (
+        pytest.param("python", marks = pytest.mark.python),
+        pytest.param("c", marks = pytest.mark.c),
+        pytest.param("fortran", marks = [
+            pytest.mark.skip(reason="Can't print NaN in Fortran"),
+            pytest.mark.fortran])
+    )
+)
+def test_print_nan(language):
+    types = str
+    pyccel_test("scripts/print_nan.py", language=language, output_dtype=types)
+
 #------------------------------------------------------------------------------
 def test_print_integers(language):
     types = str