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Defined in header <math.h> | ||
float scalbnf(float arg,intexp); | (1) | (since C99) |
double scalbn(double arg,intexp); | (2) | (since C99) |
longdouble scalbnl(longdouble arg,intexp); | (3) | (since C99) |
Defined in header <tgmath.h> | ||
#define scalbn( arg, exp ) | (4) | (since C99) |
Defined in header <math.h> | ||
float scalblnf(float arg,longexp); | (5) | (since C99) |
double scalbln(double arg,longexp); | (6) | (since C99) |
longdouble scalblnl(longdouble arg,longexp); | (7) | (since C99) |
Defined in header <tgmath.h> | ||
#define scalbln( arg, exp ) | (8) | (since C99) |
scalbnl orscalblnl is called. Otherwise, ifarg has integer type or the typedouble,scalbn orscalbln is called. Otherwise,scalbnf orscalblnf is called, respectively.Contents |
| arg | - | floating-point value |
| exp | - | integer value |
If no errors occur,arg multiplied byFLT_RADIX to the power ofexp (arg×FLT_RADIXexp
) is returned.
If a range error due to overflow occurs,±HUGE_VAL,±HUGE_VALF, or±HUGE_VALL is returned.
If a range error due to underflow occurs, the correct result (after rounding) is returned.
Errors are reported as specified inmath_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
arg is returned, unmodified.On binary systems (whereFLT_RADIX is2),scalbn is equivalent toldexp.
Althoughscalbn andscalbln are specified to perform the operation efficiently, on many implementations they are less efficient than multiplication or division by a power of two using arithmetic operators.
Thescalbln function is provided because the factor required to scale from the smallest positive floating-point value to the largest finite one may be greater than32767, the standard-guaranteedINT_MAX. In particular, for the 80-bitlongdouble, the factor is32828.
#include <errno.h>#include <fenv.h>#include <float.h>#include <math.h>#include <stdio.h> // #pragma STDC FENV_ACCESS ON int main(void){printf("scalbn(7, -4) = %f\n", scalbn(7,-4));printf("scalbn(1, -1074) = %g (minimum positive subnormal double)\n", scalbn(1,-1074));printf("scalbn(nextafter(1,0), 1024) = %g (largest finite double)\n", scalbn(nextafter(1,0),1024)); // special valuesprintf("scalbn(-0, 10) = %f\n", scalbn(-0.0,10));printf("scalbn(-Inf, -1) = %f\n", scalbn(-INFINITY,-1)); // error handlingerrno=0;feclearexcept(FE_ALL_EXCEPT);printf("scalbn(1, 1024) = %f\n", scalbn(1,1024));if(errno==ERANGE)perror(" errno == ERANGE");if(fetestexcept(FE_OVERFLOW))puts(" FE_OVERFLOW raised");}
Possible output:
scalbn(7, -4) = 0.437500scalbn(1, -1074) = 4.94066e-324 (minimum positive subnormal double)scalbn(nextafter(1,0), 1024) = 1.79769e+308 (largest finite double)scalbn(-0, 10) = -0.000000scalbn(-Inf, -1) = -infscalbn(1, 1024) = inf errno == ERANGE: Numerical result out of range FE_OVERFLOW raised
(C99)(C99) | breaks a number into significand and a power of2 (function)[edit] |
(C99)(C99) | multiplies a number by2 raised to a power (function)[edit] |
C++ documentation forscalbn | |
