log10517

#include <80c517.h>

float log10517 (
  float val);      /* value to take common logarithm of */

The log10517 function calculates the common logarithm for the floating-point number val. The logarithm is the exponent to which the base (10 in the case of common logs) must be raised to equal val. Or,

log₁₀ 10^x = val

For example,

log10517(120)
= log10517(10² × 1.2)
= 2 + log10517(1.2)
≈ 2 + 0.079181 or 2.079181

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 log10517 function returns the floating-point common logarithm of val.

• If x < 0, log10517 returns NaN.
• If x = 0, log10517 returns -INF.

exp, exp517, log, log10, log517, pow

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

void tst_log10517 (void) {
  float x;
  float y;

  x = 2.718282;
  x *= x;

  y = log10517 (x); /* y = 2 */

  printf ("LOG10517(%f) = %f\n", x, y);
}