kdeps-tools-calculator

version: 2.0.0
description: Evaluate a mathematical expression and return the result. Accepts numbers, + - * / // % **, parentheses and the math module's functions and constants (e.g. '2 + 2', '3.14 * 10**2', 'sqrt(16)', 'log(8, 2)', 'pi').
constraints: arithmetic only; no variables, strings or assignments; exponents above 10000 are rejected
outputFormat: the result as a number
parameters:
  expression:
    type: string
    description: The mathematical expression to evaluate
    required: true
python:
  script: |
    import ast, json, math, operator, sys

    a = json.loads(sys.argv[1])
    expr = str(a.get("expression") or "").strip()
    if not expr:
        sys.exit("calculator: expression is required")

    OPS = {
        ast.Add: operator.add, ast.Sub: operator.sub, ast.Mult: operator.mul,
        ast.Div: operator.truediv, ast.FloorDiv: operator.floordiv,
        ast.Mod: operator.mod, ast.Pow: operator.pow,
        ast.USub: operator.neg, ast.UAdd: operator.pos,
    }
    NAMES = {k: getattr(math, k) for k in dir(math) if not k.startswith("_")}
    NAMES.update(abs=abs, round=round, min=min, max=max, int=int, float=float)

    def ev(n):
        if isinstance(n, ast.Constant) and type(n.value) in (int, float):
            return n.value
        if isinstance(n, ast.BinOp) and type(n.op) in OPS:
            left, right = ev(n.left), ev(n.right)
            # 9**9**9 would run for hours; no real calculation needs it.
            if isinstance(n.op, ast.Pow) and abs(right) > 10000:
                raise ValueError("exponent %s is too large" % right)
            return OPS[type(n.op)](left, right)
        if isinstance(n, ast.UnaryOp) and type(n.op) in OPS:
            return OPS[type(n.op)](ev(n.operand))
        if isinstance(n, ast.Name) and n.id in NAMES and not callable(NAMES[n.id]):
            return NAMES[n.id]
        if (isinstance(n, ast.Call) and isinstance(n.func, ast.Name)
                and callable(NAMES.get(n.func.id)) and not n.keywords):
            return NAMES[n.func.id](*[ev(x) for x in n.args])
        raise ValueError("unsupported expression: %s" % ast.unparse(n))

    try:
        print(ev(ast.parse(expr, mode="eval").body))
    except Exception as e:
        sys.exit("calculator: %s" % e)