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1 files changed, 37 insertions, 0 deletions

diff --git a/ql/ast/visitors/expression_evaluator.py b/ql/ast/visitors/expression_evaluator.py
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+++ b/ql/ast/visitors/expression_evaluator.py
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+from multimethods import multimethod
+
+from ql.ast.nodes.expressions.binary_operators.binary_operator import BinaryOperatorNode
+from ql.ast.nodes.expressions.literals.literal import LiteralNode
+from ql.ast.nodes.expressions.unary_operators.unary_operator import UnaryOperatorNode
+from ql.ast.nodes.expressions.variable import VariableNode
+from ql.types.undefined import QLUndefined
+
+
+class ExpressionEvaluator:
+    def __init__(self, form):
+        self.form = form
+        self.result = QLUndefined()
+
+    @multimethod(BinaryOperatorNode)
+    def visit(self, node):
+        node.left_expression.accept(self)
+        node.right_expression.accept(self)
+        node.evaluate()
+        self.result = node.value
+
+    @multimethod(UnaryOperatorNode)
+    def visit(self, node):
+        node.expression.accept(self)
+        node.evaluate()
+        self.result = node.value
+
+    @multimethod(LiteralNode)
+    def visit(self, node):
+        self.result = node.value
+
+    @multimethod(VariableNode)
+    def visit(self, node):
+        for question in self.form.block:
+            if node.identifier == question.identifier:
+                node.value = question.answer.value
+                self.result = node.value