mh
/
qmk_firmware
mirror of https://github.com/qmk/qmk_firmware/


								"""Parse arbitrary math equations in a safe way.


								Gratefully copied from https://stackoverflow.com/a/9558001

								"""

								import ast

								import operator as op


								# supported operators

								operators = {ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul, ast.Div: op.truediv, ast.Pow: op.pow, ast.BitXor: op.xor, ast.USub: op.neg}


								def compute(expr):

								    """Parse a mathematical expression and return the answer.


								    >>> compute('2^6')

								    4

								    >>> compute('2**6')

								    64

								    >>> compute('1 + 2*3**(4^5) / (6 + -7)')

								    -5.0

								    """

								    return _eval(ast.parse(expr, mode='eval').body)


								def _eval(node):

								    if isinstance(node, ast.Num):  # <number>

								        return node.n

								    elif isinstance(node, ast.BinOp):  # <left> <operator> <right>

								        return operators[type(node.op)](_eval(node.left), _eval(node.right))

								    elif isinstance(node, ast.UnaryOp):  # <operator> <operand> e.g., -1

								        return operators[type(node.op)](_eval(node.operand))

								    else:

								        raise TypeError(node)