cbrt, cbrtf, cbrtl

< c‎ | numeric‎ | math
Common mathematical functions
Basic operations
Exponential functions
Power functions
Trigonometric and hyperbolic functions
Error and gamma functions
Nearest integer floating point operations
Floating point manipulation functions
Macro constants
Defined in header <math.h>
float       cbrtf( float arg );
(1) (since C99)
double      cbrt( double arg );
(2) (since C99)
long double cbrtl( long double arg );
(3) (since C99)
Defined in header <tgmath.h>
#define cbrt( arg )
(4) (since C99)
1-3) Computes the cubic root of arg.
4) Type-generic macro: If arg has type long double, cbrtl is called. Otherwise, if arg has integer type or the type double, cbrt is called. Otherwise, cbrtf is called.


[edit] Parameters

arg - floating point value

[edit] Return value

If no errors occur, the cubic root of arg (3arg), is returned.

If a range error occurs due to underflow, the correct result (after rounding) is returned.

[edit] Error handling

Errors are reported as specified in math_errhandling.

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

  • if the argument is ±0 or ±∞, it is returned, unchanged
  • if the argument is NaN, NaN is returned.

[edit] Notes

cbrt(arg) is not equivalent to pow(arg, 1.0/3) because the rational number
is typically not equal to 1.0/3 and std::pow cannot raise a negative base to a fractional exponent. Moreover, cbrt(arg) usually gives more accurate results than pow(arg, 1.0/3) (see example).

[edit] Example

#include <stdio.h>
#include <float.h>
#include <math.h>
int main(void)
    // normal use
    printf("cbrt(729) = %f\n", cbrt(729));
    printf("cbrt(-0.125) = %f\n", cbrt(-0.125));
    // special values
    printf("cbrt(-0) = %f\n", cbrt(-0.0));
    printf("cbrt(+inf) = %f\n", cbrt(INFINITY));
    // accuracy
    printf("cbrt(343)      = %.*f\n", DBL_DECIMAL_DIG, cbrt(343));
    printf("pow(343,1.0/3) = %.*f\n", DBL_DECIMAL_DIG, pow(343, 1.0/3));

Possible output:

cbrt(729) = 9.000000
cbrt(-0.125) = -0.500000
cbrt(-0) = -0.000000
cbrt(+inf) = inf
cbrt(343)      = 7.00000000000000000
pow(343,1.0/3) = 6.99999999999999911

[edit] References

  • C11 standard (ISO/IEC 9899:2011):
  • The cbrt functions (p: 247)
  • 7.25 Type-generic math <tgmath.h> (p: 373-375)
  • F.10.4.1 The cbrt functions (p: 524)
  • C99 standard (ISO/IEC 9899:1999):
  • The cbrt functions (p: 228)
  • 7.22 Type-generic math <tgmath.h> (p: 335-337)
  • F.9.4.1 The cbrt functions (p: 460)

[edit] See also

computes a number raised to the given power (xy)
(function) [edit]
computes square root (x)
(function) [edit]
computes square root of the sum of the squares of two given numbers (x2
(function) [edit]