从int转换为char

Question

I'd like to know how this cast works :

int value = 100;
auto f = [&value] (int x, int y) -> char { return x + y + value; };
printf("%d\n", f(10, 20));
value = 200;
printf("%d\n", f(10, 20));
return 0;

It prints -126 and -30 but i don't understand how is it possible to print a negative integer.

Answer 1

The numerical range for char is -128 .. 127 . 10 + 20 + 100 is 130 and outside of that range, so it wraps around when expressed as char .

To fix you need to use a data type that can contain values large enough:

auto f = [&value] (int x, int y) -> int { return x + y + value; };

Or use values < 127.