log517

#include <80c517.h>

float log517 (
  float val);      /* value to take natural logarithm of */

The log517 function calculates the natural logarithm for the floating-point number val. The logarithm is the exponent to which the base (e or 2.718282... in the case of natural logs) must be raised to equal val. Or,

log_e e^x = val

Note

• This routine uses the arithmetic unit of the Infineon C517x/C509 to provide accelerated execution speed. Do not use this routine with a CPU that does not support this feature.

The log517 function returns the floating-point natural logarithm of val.

• If x < 0, log517 returns NaN.
• If x = 0, log517 returns -INF.

exp, exp517, log, log10, log10517

#include <80c517.h>
#include <stdio.h> /* for printf */

void tst_log517 (void) {
  float x;
  float y;

  x = 2.718282;
  x *= x;

  y = log517 (x); /* y = 2 */

  printf ("LOG517(%f) = %f\n", x, y);
}