Avoiding compiler issues with abs()
The function you are using is actually the integer version of abs
, and GCC does an implicit conversion to integer.
This can be verified by a simple test program:
#include <iostream>
#include <cmath>
int main()
{
double a = -5.4321;
double b = std::abs(a);
double c = abs(a);
std::cout << "a = " << a << ", b = " << b << ", c = " << c << '\n';
}
Output is:
a = -5.4321, b = 5.4321, c = 5
To get a warning about this, use the -Wconversion
flag to g++. Actually, the GCC documentation for that option explicitly mentions calling abs
when the argument is a double
. All warning options can be found here.
Be warned, you don't need to explicitly #include <cmath>
, <iostream>
does the damage as well (and maybe some other headers). Also, note that -Wall
doesn't give you any warnings about it.
#include <iostream>
int main() {
std::cout << abs(.5) << std::endl;
std::cout << typeid(decltype(abs)).name() << std::endl;
}
Gives output
0
FiiE
On
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04)