Absolute Value - The GNU C Library

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#### 20.8.1 Absolute Value

These functions are provided for obtaining the absolute value (or magnitude) of a number. The absolute value of a real number x is x if x is positive, −x if x is negative. For a complex number z, whose real part is x and whose imaginary part is y, the absolute value is `sqrt (`x`*`x`+` y`*`y`)`.

Prototypes for `abs`, `labs` and `llabs` are in `stdlib.h`; `imaxabs` is declared in `inttypes.h`; `fabs`, `fabsf` and `fabsl` are declared in `math.h`. `cabs`, `cabsf` and `cabsl` are declared in `complex.h`.

— Function: int abs (int number)

> — Function: long int labs (long int number)

> > — Function: long long int llabs (long long int number)

> > > — Function: intmax_t imaxabs (intmax_t number)

> > > > These functions return the absolute value of number.

> > > > Most computers use a two's complement integer representation, in which the absolute value of `INT_MIN` (the smallest possible `int`) cannot be represented; thus, `abs (INT_MIN)` is not defined.

> > > > `llabs` and `imaxdiv` are new to ISO C99.

> > > > See Integers for a description of the `intmax_t` type.

— Function: double fabs (double number)

> — Function: float fabsf (float number)

> > — Function: long double fabsl (long double number)

> > > This function returns the absolute value of the floating-point number number.

— Function: double cabs (complex double z)

> — Function: float cabsf (complex float z)

> > — Function: long double cabsl (complex long double z)

> > > These functions return the absolute value of the complex number z (see Complex Numbers). The absolute value of a complex number is:

> > >               sqrt (creal (z) * creal (z) + cimag (z) * cimag (z))

> > > This function should always be used instead of the direct formula because it takes special care to avoid losing precision. It may also take advantage of hardware support for this operation. See `hypot` in Exponents and Logarithms.