fabs

fabs

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Obtains the absolute value of a number

 #include <math.h> double fabs ( double x  ); float fabsf ( float x  ); long double fabsl ( long double x  ); 

The fabs( ) function returns the absolute value of its floating-point argument x; if x is greater than or equal to 0, the return value is equal to x. If x is less than 0, the function returns -x.

Example

 float x = 4.0F * atanf( 1.0F ); long double y = 4.0L * atanl( 1.0L ); if ( x == y )   printf( "x and y are exactly equal.\n" ); else if ( fabs( x - y ) < 0.0001 * fabsl( y ) )   printf( "x and y are approximately equal:\n"           "x is %.8f; y is %.8Lf.\n", x, y ); 

This code produces the following output:

 x and y are approximately equal: x is 3.14159274; y is 3.14159265. 

See Also

The absolute value functions for integer types: abs( ), labs( ), llabs( ), and imaxabs( ); the absolute value functions for complex numbers: cabs( ), cabsf( ), cabsl( ); the C99 functions fdim( ) and copysign( ); the functions fmax( ) and fmin( )