#!/usr/bin/env python3
import sys
from calc.lexer import tokenize, LexError
from calc.parser import parse, ParseError
from calc.evaluator import evaluate, EvalError


def main():
    if len(sys.argv) != 2:
        print("usage: calc.py <expression>", file=sys.stderr)
        sys.exit(1)
    expr = sys.argv[1]
    try:
        result = evaluate(parse(tokenize(expr)))
    except (LexError, ParseError, EvalError) as e:
        print(f"error: {e}", file=sys.stderr)
        sys.exit(1)
    print(result)


if __name__ == '__main__':
    main()