signbit()

The signbit() function returns true if the sign of the argument is negative and false if its sign is positive.

The cmath library must be added at the top of the file.

std::signbit(n);

Argument n must be of type double/float/long double/int, and the return value will be of that type. This function also detects the signs of zeroes, infinities, and NaNs.

#include <iostream>
#include <cmath>

int main() {
  double a = 9.0, b = 0.0;
  double c = a/b;

  // If c is false, print out that it tends to positive infinity.
  if (std::signbit(c) == false) {
    std::cout << "c tends to positive infinity";
  }
  else {
    std::cout << "c tends to negative infinity";
  }
  return 0;
}

In the example above, c is infinity because a number divided by 0 evaluates to positive infinity when there is a limit.

This will output:

c tends to positive infinity

The example below outputs a string about whether the integer is positive or negative:

Code
Output
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