38 lines
1.1 KiB
Python
38 lines
1.1 KiB
Python
from calc.parser import Num, BinOp, Unary
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class EvalError(Exception):
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pass
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def evaluate(node):
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"""Walk the AST and return int | float.
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Whole-valued results (including whole-valued division) are returned as int;
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non-whole float results are returned as float.
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"""
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if isinstance(node, Num):
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return node.value
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if isinstance(node, Unary):
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if node.op == '-':
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return -evaluate(node.operand)
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raise EvalError(f"unknown unary op {node.op!r}")
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if isinstance(node, BinOp):
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left = evaluate(node.left)
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right = evaluate(node.right)
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if node.op == '+':
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return left + right
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if node.op == '-':
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return left - right
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if node.op == '*':
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return left * right
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if node.op == '/':
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if right == 0:
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raise EvalError("division by zero")
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result = left / right
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if result == int(result):
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return int(result)
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return result
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raise EvalError(f"unknown binary op {node.op!r}")
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raise EvalError(f"unknown node type {type(node).__name__!r}")
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