ios - 带有分数的 NSDecimalNumber 在提升到高幂时返回大数？

Question

好的，所以我正在尝试将这个小数额提高到一个高幂。但出于某种原因，根据日志，我得到了一个非常高的数字，有时甚至是一个 NSDecimalOverflor 错误。有人可以帮我解决这个问题吗？

NSDecimalNumber *number = [[NSDecimalNumber alloc] initWithDouble:0.4];
NSInteger power = 1001;

number = [number decimalNumberByRaisingToPower:power];

NSLog(@"%@",number);

也许我因为数字太小而达到了某种极限？任何事情都会有所帮助!

编辑:哦，堆栈跟踪显示所有数字在实际上下文中中断时都是相同的。

Answer 1

来自苹果文档:

NSDecimalNumber, an immutable subclass of NSNumber, provides an object-oriented wrapper for doing base-10 arithmetic. An instance can represent any number that can be expressed as mantissa x 10^exponent where mantissa is a decimal integer up to 38 digits long, and exponent is an integer from –128 through 127.

所以有一个限制，考虑浮点double。

0.4^1001:
4e-399
或者
0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001

这比 NSDecimalNumber 可以处理的要大得多。