Create evaluator for minus operator

smnp/runtime/evaluators/minus.py

@@ -0,0 +1,31 @@
+from smnp.error.runtime import RuntimeException
+from smnp.runtime.evaluator import Evaluator, evaluate
+from smnp.type.model import Type
+
+
+class MinusEvaluator(Evaluator):
+
+    @classmethod
+    def evaluator(cls, node, environment):
+        value = evaluate(node.value, environment).value
+        try:
+            return {
+                Type.INTEGER: cls.evaluateForInteger,
+                Type.STRING: cls.evaluateForString,
+                Type.LIST: cls.evaluateForList
+            }[value.type](value.value)
+        except KeyError:
+            raise RuntimeException(f"Type {value.type.name.lower()} does not support '{node.operator.value}' operator", node.pos)
+
+    @classmethod
+    def evaluateForInteger(cls, value):
+
+        return Type.integer(-value)
+
+    @classmethod
+    def evaluateForString(cls, value):
+        return Type.string(value[::-1])
+
+    @classmethod
+    def evaluateForList(cls, value):
+        return Type.list(value[::-1])