cheader.py 文件源码

def eval_expr(expr):

    """ Eval and expression inside a #define using a suppart of python grammar """

    def _eval(node):
        if isinstance(node, ast.Num):
            return node.n
        elif isinstance(node, ast.BinOp):
            return OPERATORS[type(node.op)](_eval(node.left), _eval(node.right))
        elif isinstance(node, ast.UnaryOp):
            return OPERATORS[type(node.op)](_eval(node.operand))
        elif isinstance(node, ast.BoolOp):
            values = [_eval(x) for x in node.values]
            return OPERATORS[type(node.op)](**values)
        else:
            raise TypeError(node)

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