interpreter.py

from nodes import *
from values import Number

class Interpreter:
  def visit(self, node):
    method_name = f'visit_{type(node).__name__}'
    method = getattr(self, method_name)
    return method(node)

  def visit_NumberNode(self, node):
    return Number(node.value)

  def visit_AddNode(self, node):
    return Number(self.visit(node.node_a).value + self.visit(node.node_b).value)

  def visit_SubtractNode(self, node):
    return Number(self.visit(node.node_a).value - self.visit(node.node_b).value)

  def visit_MultiplyNode(self, node):
    return Number(self.visit(node.node_a).value * self.visit(node.node_b).value)

  def visit_DivideNode(self, node):
    try:
      return Number(self.visit(node.node_a).value / self.visit(node.node_b).value)
    except:
      raise Exception("Runtime math error")

  def visit_PlusNode(self, node):
    return self.visit(node.node)

  def visit_MinusNode(self, node):
    return Number(-self.visit(node.node).value)