log10, log10f, log10l

 

C

Language

Standard Library

Type support

Dynamic memory management

Error handling

Program utilities

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

 

Numerics

Common mathematical functions

Floating-point environment

Complex number arithmetics

Random number generation

Type-generic math

 

Common mathematical functions

Functions
Basic operations
abslabsllabsimaxabs (C99) fabs divldivlldivimaxdiv (C99) fmod	remainder (C99) remquo (C99) fma (C99) fmax (C99) fmin (C99) fdim (C99) nannanfnanl (C99)(C99)(C99)
Exponential functions
exp exp2 (C99) expm1 (C99)	log log10 log1p (C99) log2 (C99)
Power functions
sqrt cbrt (C99)	hypot (C99) pow
Trigonometric and hyperbolic functions
sin cos tan asin acos atan atan2	sinh cosh tanh asinh (C99) acosh (C99) atanh (C99)
Error and gamma functions
erf (C99) erfc (C99)	lgamma (C99) tgamma (C99)
Nearest integer floating point operations
ceil floor roundlroundllround (C99)(C99)(C99)	trunc (C99) nearbyint (C99) rintlrintllrint (C99)(C99)(C99)
Floating point manipulation functions
ldexp scalbnscalbln (C99)(C99) ilogb (C99) logb (C99)	frexp modf nextafternexttoward (C99)(C99) copysign (C99)
Classification
fpclassify (C99)
isfinite (C99)
isinf (C99)
isnan (C99)
isnormal (C99)
signbit (C99)
Macro constants
HUGE_VALFHUGE_VALHUGE_VALL (C99)(C99)	FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99)

 

Defined in header <math.h>
float       log10f( float arg );	(1)	(since C99)
double      log10( double arg );	(2)
long double log10l( long double arg );	(3)	(since C99)
Defined in header <tgmath.h>
#define log10( arg )	(4)	(since C99)

1-3) Computes the common (base-10) logarithm of arg.

4) Type-generic macro: If arg has type long double, log10l is called. Otherwise, if arg has integer type or the type double, log10 is called. Otherwise, log10f is called.

Parameters

arg

-

floating point value

Return value

If no errors occur, the common (base-10) logarithm of arg (log
10(arg) or lg(arg)) is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported)

If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.

Error handling

Errors are reported as specified in math_errhandling

Domain error occurs if arg is less than zero.

Pole error may occur if arg is zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
• If the argument is 1, +0 is returned
• If the argument is negative, NaN is returned and FE_INVALID is raised.
• If the argument is +∞, +∞ is returned
• If the argument is NaN, NaN is returned

Example

Run this code

#include <stdio.h>
#include <math.h>
#include <float.h>
#include <errno.h>
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
int main(void)
{
    printf("log10(1000) = %f\n", log10(1000));
    printf("log10(0.001) = %f\n", log10(0.001));
    printf("base-5 logarithm of 125 = %f\n", log10(125)/log10(5));
    // special values
    printf("log10(1) = %f\n", log10(1));
    printf("log10(+Inf) = %f\n", log10(INFINITY));
    //error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("log10(0) = %f\n", log10(0));
    if(errno == ERANGE) perror("    errno == ERANGE");
    if(fetestexcept(FE_DIVBYZERO)) puts("    FE_DIVBYZERO raised");
}

Possible output:

log10(1000) = 3.000000
log10(0.001) = -3.000000
base-5 logarithm of 125 = 3.000000
log10(1) = 0.000000
log10(+Inf) = inf
log10(0) = -inf
    errno == ERANGE: Numerical result out of range
    FE_DIVBYZERO raised

See also

loglogflogl (C99)(C99)	computes natural (base-e) logarithm (ln(x)) (function)
log2log2flog2l (C99)(C99)(C99)	computes base-2 logarithm (log2(x)) (function)
log1plog1pflog1pl (C99)(C99)(C99)	computes natural (base-e) logarithm of 1 plus the given number (ln(1+x)) (function)
C++ documentation for log10