Enable creating custom methods

smnp/runtime/evaluators/extend.py

@@ -0,0 +1,25 @@
+from smnp.runtime.evaluator import Evaluator
+from smnp.runtime.evaluators.function import argumentsNodeToMethodSignature
+from smnp.runtime.evaluators.type import TypeEvaluator
+
+
+class ExtendEvaluator(Evaluator):
+
+    @classmethod
+    def evaluator(cls, node, environment):
+        type = TypeEvaluator.evaluate(node.type, environment).value #TODO check if it isn't necessary to verify 'result' attr of EvaluatioNResult
+        variable = node.variable.value
+        cls._evaluateExtend(node.methods, environment, type, variable)
+
+    @classmethod
+    def _evaluateExtend(cls, node, environment, type, variable):
+        for child in node.children:
+            cls._evaluateMethodDefinition(child, environment, type, variable)
+
+    @classmethod
+    def _evaluateMethodDefinition(cls, node, environment, type, variable):
+        name = node.name.value
+        signature = argumentsNodeToMethodSignature(node.arguments)
+        arguments = [arg.variable.value for arg in node.arguments]
+        body = node.body
+        environment.addCustomMethod(type, variable, name, signature, arguments, body)