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log10

You can use the log10 function to compute the common logarithm of a real number.

double_t log10 (double_t x);

x

Any positive floating-point number.

DESCRIPTION

The log10 function returns the common (base 10) logarithm of its argument.

$log10(x)\; =\; log$₁₀x = y such that $x\; =\; 10y$

EXCEPTIONS

When x is finite and nonzero, the result of $log10(x)$ might raise one of the following exceptions:

• inexact (for all finite, nonzero values of x other than +1)
• invalid (when x is negative)

SPECIAL CASES

Table 10-15 shows the results when the argument to the log10 function is a zero, a NaN, or an Infinity, plus other special cases for the log10 function.

Special cases for the log10 function

Operation	Result	Exceptions raised
$log10(x)$ for x < 0	NaN	Invalid
$log10(+1)$	+0	None
$log10(+0)$	-	Divide-by-zero
$log10(-0)$	-	Divide-by-zero
$log10(NaN)$	NaN	None[36]
$log10(+$ )	+	None
$log10(-$ )	NaN	Invalid

EXAMPLES

z = log10(+1.0);  /* z = 0.0 because 100 = 1 */
z = log10(10.0);  /* z = 1.0 because 101 = 10. The inexact 
                     exception is raised. */
z = log10(-1.0);  /* z = NAN because negative arguments are not 
                     allowed. The invalid exception is raised. */

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[36] If the NaN is a signaling NaN, the invalid exception is raised.