const_fold.py 文件源码

def check_pow(config, num, exp, mod=None):
    if num == 0 and exp < 0:
        # 0 ** -1 raises a ZeroDivisionError
        return False

    if num < 0 and exp < 1.0 and exp != 0.0:
        # pow(-25, 0.5) raises a ValueError
        return False

    if mod is not None:
        # pow(a, b, m) only works if a and b are integers
        if not isinstance(num, int):
            return False
        if not isinstance(exp, int):
            return False

        if mod == 0:
            # pow(2, 1024, 0) raises a ValueError:
            # 'pow() 3rd argument cannot be 0'
            return False

    if (isinstance(num, int)
       and isinstance(exp, int)
       # don't call log2(0) (error)
       and num != 0
       # if exp < 0, the result is a float which has a fixed size
       and exp > 0):
        # bits(num ** exp) = log2(num) * exp
        if math.log2(abs(num)) * exp >= config.max_int_bits:
            # pow() result will be larger than max_constant_size.
            return False

    return True