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Load the exponent of a radix-independent floating point number
#include <math.h>
double scalb( double x,
double n );
- x
- The floating point number that you want to multiply by the exponent.
- n
- The exponent to apply to the radix of the machine's floating-point
arithmetic.
libm
Use the -l m option to
qcc
to link against this library.
These functions compute x × rn,
where r is the radix
of the machine's floating point arithmetic
and n is a finite number. When r is 2,
scalb() is equivalent to
ldexp().
|
We recommend that you use
scalbn()
because it computes by manipulating exponents, instead of using mock
multiplications or additions. |
x × rn
|
If an error occurs, these functions return 0, but this is also a valid
mathematical result.
If you want to check for errors, set
errno
to 0, call the function, and then check errno again.
These functions don't change errno if no errors occurred. |
#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <math.h>
#include <fpstatus.h>
int main(int argc, char** argv)
{
double a, b, c, d;
a = 10;
b = 2;
c = scalb(a, b);
d = sqrt(c/a);
printf("Radix of machines fp arithmetic is %f \n", d);
printf("So %f = %f * (%f ^ %f) \n", c, a, d, b);
return(0);
}
produces the output:
Radix of machines fp arithmetic is 2.000000
So 40.000000 = 10.000000 * (2.000000 ^ 2.000000)
POSIX 1003.1 XSI
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
ldexp(),
scalbn()
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