add pi predefined constant (#1075)

Co-authored-by: C.A.P. Linssen <charl@turingbirds.com>

doc/nestml_language/nestml_language_concepts.rst

@@ -579,6 +579,8 @@ The following variables and constants are predefined in NESTML and can be used o
      - The current simulation time (read only)
    * - ``e``
      - Euler's constant (2.718...)
+   * - ``pi``
+     - pi (3.14159...)
    * - ``inf``
      - Floating point infinity
 

pynestml/codegeneration/printers/cpp_variable_printer.py

@@ -49,6 +49,9 @@ def print_variable(self, node: ASTVariable) -> str:
         assert isinstance(node, ASTVariable)
 
         if node.get_name() == PredefinedVariables.E_CONSTANT:
-            return "numerics::e"
+            return "2.718281828459045235360287471352"    # not defined in C++11 stdlib
+
+        if node.get_name() == PredefinedVariables.E_CONSTANT:
+            return "M_PI"    # from <cmath>
 
         return CppVariablePrinter._print_cpp_name(node.get_complete_name())

pynestml/codegeneration/printers/nest_variable_printer.py

@@ -72,7 +72,10 @@ def print_variable(self, variable: ASTVariable) -> str:
             return "((post_neuron_t*)(__target))->get_" + _name + "(_tr_t)"
 
         if variable.get_name() == PredefinedVariables.E_CONSTANT:
-            return "numerics::e"
+            return "numerics::e"    # from nest::
+
+        if variable.get_name() == PredefinedVariables.PI_CONSTANT:
+            return "numerics::pi"    # from nest::
 
         if variable.get_name() == PredefinedVariables.TIME_CONSTANT:
             return "get_t()"

pynestml/codegeneration/printers/python_stepping_function_variable_printer.py

@@ -42,6 +42,9 @@ def print_variable(self, node: ASTVariable) -> str:
         if node.get_name() == PredefinedVariables.E_CONSTANT:
             return "np.e"
 
+        if node.get_name() == PredefinedVariables.PI_CONSTANT:
+            return "np.pi"
+
         symbol = node.get_scope().resolve_to_symbol(node.get_complete_name(), SymbolKind.VARIABLE)
 
         if symbol.is_state() and not symbol.is_inline_expression:

pynestml/codegeneration/printers/python_variable_printer.py

@@ -74,6 +74,9 @@ def print_variable(self, variable: ASTVariable) -> str:
         if variable.get_name() == PredefinedVariables.E_CONSTANT:
             return "math.e"
 
+        if variable.get_name() == PredefinedVariables.PI_CONSTANT:
+            return "math.pi"
+
         symbol = variable.get_scope().resolve_to_symbol(variable.get_complete_name(), SymbolKind.VARIABLE)
         if symbol is None:
             # test if variable name can be resolved to a type

pynestml/codegeneration/printers/spinnaker_c_variable_printer.py

@@ -63,6 +63,9 @@ def print_variable(self, variable: ASTVariable) -> str:
         if variable.get_name() == PredefinedVariables.E_CONSTANT:
             return "REAL_CONST(2.718282)"
 
+        if variable.get_name() == PredefinedVariables.PI_CONSTANT:
+            return "REAL_CONST(3.14159)"
+
         symbol = variable.get_scope().resolve_to_symbol(variable.get_complete_name(), SymbolKind.VARIABLE)
         if symbol is None:
             # test if variable name can be resolved to a type

pynestml/symbols/predefined_variables.py

@@ -29,9 +29,10 @@ class PredefinedVariables:
     """
     This class is used to store all predefined variables as generally available.
     """
-    name2variable = {}   # type: Mapping[str, VariableSymbol]
-    E_CONSTANT = 'e'     # type: str
-    TIME_CONSTANT = 't'  # type: str
+    name2variable: Mapping[str, VariableSymbol] = {}
+    E_CONSTANT: str = 'e'
+    PI_CONSTANT: str = 'pi'
+    TIME_CONSTANT: str = 't'
 
     @classmethod
     def register_variables(cls):
@@ -40,6 +41,7 @@ def register_variables(cls):
         """
         cls.name2variable = {}
         cls.__register_euler_constant()
+        cls.__register_pi_constant()
         cls.__register_time_constant()
 
     @classmethod
@@ -53,7 +55,6 @@ def __register_predefined_type_variables(cls):
                                     type_symbol=PredefinedTypes.get_type(name),
                                     variable_type=VariableType.TYPE)
             cls.name2variable[name] = symbol
-        return
 
     @classmethod
     def __register_euler_constant(cls):
@@ -64,7 +65,16 @@ def __register_euler_constant(cls):
                                 is_predefined=True, type_symbol=PredefinedTypes.get_real_type(),
                                 variable_type=VariableType.VARIABLE)
         cls.name2variable[cls.E_CONSTANT] = symbol
-        return
+
+    @classmethod
+    def __register_pi_constant(cls):
+        """
+        Adds the pi constant.
+        """
+        symbol = VariableSymbol(name='pi', block_type=BlockType.STATE,
+                                is_predefined=True, type_symbol=PredefinedTypes.get_real_type(),
+                                variable_type=VariableType.VARIABLE)
+        cls.name2variable[cls.PI_CONSTANT] = symbol
 
     @classmethod
     def __register_time_constant(cls):
@@ -75,7 +85,6 @@ def __register_time_constant(cls):
                                 is_predefined=True, type_symbol=PredefinedTypes.get_type('ms'),
                                 variable_type=VariableType.VARIABLE)
         cls.name2variable[cls.TIME_CONSTANT] = symbol
-        return
 
     @classmethod
     def get_time_constant(cls):
@@ -106,8 +115,8 @@ def get_variable(cls, name):
         """
         if name in cls.name2variable.keys():
             return cls.name2variable[name]
-        else:
-            return None
+
+        return None
 
     @classmethod
     def get_variables(cls):

tests/resources/ExpressionCollection.nestml

@@ -152,6 +152,9 @@ model ExpressionCollection:
         testerf real = erf(0.)
         testerfc real = erfc(0.)
 
+        test_e real = e
+        test_pi real = pi
+
     equations:
         #neuron aeif_cond_alpha_neuron
         test0 = E_L