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scalbn, scalbln

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< c‎ | numeric‎ | math
Revision as of 08:17, 17 April 2014 by Newatthis (Talk | contribs)

 
 
 
Common mathematical functions
Functions
Basic operations
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(C99)
(C99)
(C99)(C99)(C99)
Exponential functions
(C99)
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(C99)
Power functions
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Trigonometric and hyperbolic functions
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Error and gamma functions
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Nearest integer floating point operations
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Floating point manipulation functions
scalbnscalbln
(C99)(C99)
(C99)
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Classification
(C99)
(C99)
(C99)
Macro constants
 
Defined in header <math.h>
float       scalbnf( float arg, int exp );
(since C99)
double      scalbn( double arg, int exp );
(since C99)
long double scalbnl( long double arg, int exp );
(since C99)
float       scalblnf( float arg, long exp );
(since C99)
double      scalbln( double arg, long exp );
(since C99)
long double scalblnl( long double arg, long exp );
(since C99)

Multiplies a floating point value arg by FLT_RADIX raised to power exp. On binary systems it is equivalent to ldexp().

Contents

Parameters

arg - floating point value
exp - integer value

Return value

Returns arg×FLT_RADIXexp.

If the result is too large for the underlying type, range error occurs and HUGE_VAL is returned.

Example

#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <errno.h>
#include <float.h>
#include <string.h>
 
#pragma STDC FENV_ACCESS ON
 
void show_fe_exceptions(void)
{
    printf("current exceptions raised: ");
    if(fetestexcept(FE_DIVBYZERO))     printf(" FE_DIVBYZERO");
    if(fetestexcept(FE_INEXACT))       printf(" FE_INEXACT");
    if(fetestexcept(FE_INVALID))       printf(" FE_INVALID");
    if(fetestexcept(FE_OVERFLOW))      printf(" FE_OVERFLOW");
    if(fetestexcept(FE_UNDERFLOW))     printf(" FE_UNDERFLOW");
    if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none");
    printf("\n");
}
 
int main(void)
{
    printf("FLT_RADIX = %d\n", FLT_RADIX);
    printf("\n");
 
    printf("scalbn(1.0,+1023)   = %g\n",    scalbn(1.0,+1023));     /* 1 * 2^(+1023)  */
    printf("scalbn(1.0,-1074)   = %g\n",    scalbn(1.0,-1074));     /* 1 * 2^(-1074)  */
    printf("scalbn(5.0,0)       = %+.1f\n", scalbn(5.0,0));         /* 5 * 2^0        */
    printf("scalbn(+0.0,1)      = %+.1f\n", scalbn(+0.0,1));        /* 0 * 2^1        */
    printf("scalbn(-0.0,1)      = %+.1f\n", scalbn(-0.0,1));
    printf("scalbn(+INFINITY,1) = %+f\n",   scalbn(+INFINITY,1));   /* INFINITY * 2^1 */
    printf("scalbn(-INFINITY,1) = %+f\n",   scalbn(-INFINITY,1));
    printf("\n");
 
    /* "inexact" and "overflow" floating-point exceptions */
    /* Overflow does not set errno.                       */
    /* 1 * 2^(+1024)                                      */
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("scalbn(1.0,1024)    = %f\n",   scalbn(1.0,1024));
    printf("%s\n",strerror(errno));
    show_fe_exceptions();
    printf("\n");
 
    /* "inexact" and "underflow" floating-point exceptions */
    /* Underflow does not set errno.                       */
    /* 1 * 2^(-1075)                                       */
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("scalbn(1.0,-1075)   = %g\n",   scalbn(1.0,-1075));
    printf("%s\n",strerror(errno));
    show_fe_exceptions();
 
    return 0;
}

Possible output:

FLT_RADIX = 2
 
scalbn(1.0,1023)    = 8.98847e+307
scalbn(1.0,-1074)   = 4.94066e-324
scalbn(5.0,0)       = +5.0
scalbn(+0.0,1)      = +0.0
scalbn(-0.0,1)      = -0.0
scalbn(+INFINITY,1) = +inf
scalbn(-INFINITY,1) = -inf
 
scalbn(1.0,1024)    = inf
Success
current exceptions raised:  FE_INEXACT FE_OVERFLOW
 
scalbn(1.0,-1075)   = 0
Success
current exceptions raised:  FE_INEXACT FE_UNDERFLOW

See also

breaks a number into significand and a power of 2
(function) [edit]
multiplies a number by 2 raised to a power
(function) [edit]