当心,我在说::abs(),不是std::abs()
根据cplusplus.com网站,abs对于stdlib.h C版本应该表现不同,如果你包括<cmath>
以下是此页面的摘录(::abs不处理std::abs):
double abs (double x);
float abs (float x);
long double abs (long double x);
Compute absolute value
/*
Returns the absolute value of x: |x|.
These convenience abs overloads are exclusive of C++. In C, abs is only declared
in <cstdlib> (and operates on int values).
The additional overloads are provided in this header (<cmath>) for the integral types:
These overloads effectively …