学步园

当用abs求绝对值时，需要注意不同的数据类型调用不同的API函数，其中abs、labs、fabs分别对应整型、长整型、浮点型。假如对浮点数用了abs得到的将是强制转换后的整型。下面是MSDN上的例子：

Example

/* ABS.C: This program computes and displays
 * the absolute values of several numbers.
 */

#include  <stdio.h>
#include  <math.h>
#include  <stdlib.h>

void main( void )
{
   int    ix = -4, iy;
   long   lx = -41567L, ly;
   double dx = -3.141593, dy;

   iy = abs( ix );
   printf( "The absolute value of %d is %d/n", ix, iy);

   ly = labs( lx );
   printf( "The absolute value of %ld is %ld/n", lx, ly);

   dy = fabs( dx );
   printf( "The absolute value of %f is %f/n", dx, dy );
}

Output

The absolute value of -4 is 4
The absolute value of -41567 is 41567
The absolute value of -3.141593 is 3.141593