c++ - 无法正确比较两个数字

Question

unsigned long long value = 0;

bool result = value >= std::numeric_limits<signed int>::min();

这应该给出 true 但给出 false？为什么以及如何解决它？

Answer 1

int 转换为无符号 int 以进行比较。您可以将 unsigned long long 转换为 long long。

5/9:

Many binary operators that expect operands of arithmetic or enumeration type cause conversions and yield result types in a similar way. The purpose is to yield a common type, which is also the type of the result. This pattern is called the usual arithmetic conversions, which are defined as follows:

...

Then, if either operand is unsigned long the other shall be converted to unsigned long.

...

Otherwise, if either operand is unsigned, the other shall be converted to unsigned.

unsigned long long 和 long long 不是 c++03 中的标准类型，但编译器很可能会使用上面定义的机制来处理这些类型。然后，提到的转换规则将涵盖此特定转换。