# exp2(), exp2f(), exp2l()

QNX SDP8.0C Library ReferenceAPIDeveloper

*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
- 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., 2^{x}).

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:

Safety: | |
---|---|

Cancellation point | No |

Signal handler | Yes |

Thread | Yes |

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