Calculate the base-2 exponential of a number
Synopsis:
#include <math.h>
double exp2( double x );
float exp2f( float x );
long double exp2l(long double x );
Arguments:
- x
- The number that you want to calculate the base-2 exponential of.
Library:
- libm
- The general-purpose math library.
- libm-sve
- (QNX Neutrino 7.1 or later)
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 exp2(), exp2f(), and exp2l() functions
compute the base-2 exponential function of x (i.e., 2x).
To check for error situations, use
feclearexcept()
and
fetestexcept().
For example:
- Call feclearexcept(FE_ALL_EXCEPT) before calling
exp2(), exp2f(), or exp2l().
- On return, if fetestexcept(FE_ALL_EXCEPT)
is nonzero, then an error has occurred.
Returns:
The base-2 exponential function of x.
If x is: |
These functions return: |
Errors: |
±0.0 |
1 |
— |
A value that would cause overflow |
Inf |
FE_OVERFLOW |
A value that would cause underflow |
0.0 |
FE_UNDERFLOW |
-Inf |
0.0 |
— |
Inf |
Inf |
— |
NaN |
NaN |
— |
These functions raise FE_INEXACT if the FPU reports that
the result can't be exactly represented as a floating-point number.
Classification:
C11,
POSIX 1003.1
Safety: |
|
Cancellation point |
No |
Interrupt handler |
Yes |
Signal handler |
Yes |
Thread |
Yes |