Why use abs() or fabs() instead of conditional negation?

Question

In C/C++, why should one use abs() or fabs() to find the absolute value of a variable without using the following code?

int absoluteVal         


        

Answer 1

Why use abs() or fabs() instead of conditional negation?

Various reasons have already been stated, yet consider conditional code advantages as abs(INT_MIN) should be avoided.

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There is a good reason to use the conditional code in lieu of abs() when the negative absolute value of an integer is sought

// Negative absolute value

int nabs(int value) {
  return -abs(value);  // abs(INT_MIN) is undefined behavior.
}

int nabs(int value) {
  return value < 0 ? value : -value; // well defined for all `int`
}

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When a positive absolute function is needed and value == INT_MIN is a real possibility, abs(), for all its clarity and speed fails a corner case. Various alternatives

unsigned absoluteValue = value < 0 ? (0u - value) : (0u + value);