scalbln(), scalblnf(), scalblnl()
QNX SDP8.0C Library ReferenceAPIDeveloper
Load the exponent of a radix-independent floating point number
Synopsis:
#include <math.h>
double scalbln ( double x,
long int n );
float scalblnf ( float x,
long int n );
long double scalblnl ( long double x,
long int n );
Arguments:
- 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.
Library:
- libm
- The general-purpose math library.
- libm-sve
- A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.
Your system requirements will determine how you should work with these libraries:
- If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
- If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.
Note:
Compile your program with the -fno-builtin option to prevent the compiler from using a
built-in version of the function.
Description:
The scalbln(), scalblnf(), and scalblnl() functions compute x × rn, where r is the radix of the machine's floating-point arithmetic. The difference between the scalbn* and scalbln* functions is the type of the second argument.
To check for error situations, use feclearexcept() and fetestexcept(). For example:
- Call
feclearexcept(FE_ALL_EXCEPT)before calling scalbln(), scalblnf(), or scalblnl(). - On return, if
fetestexcept(FE_ALL_EXCEPT)is nonzero, then an error has occurred.
Returns:
x × rn
| If: | These functions return: | Errors: |
|---|---|---|
| x is NaN | NaN | — |
| x is ±0.0 or ±Inf | x | — |
| n is 0 | x | — |
| The correct value would cause underflow | The correct value, after rounding | FE_UNDERFLOW |
| The correct value would cause overflow | Inf | FE_OVERFLOW |
These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
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