feat: add math/base/special/exp2f

[aayush0325]

Resolves #649

Description

What is the purpose of this pull request?

This pull request:

• adds math/base/special/exp2f

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves [RFC]: Add C implementations to base special math functions (tracking issue) #649

Questions

Any questions for reviewers of this pull request?

What should i do about benchmark/c/cephes ? that doesn't seem to compile locally and on the CI tests as well.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[aayush0325]

/stdlib update-copyright-years

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/exp2f	$\color{green}328/328$ $\color{green}+100.00\%$	$\color{green}19/19$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}328/328$ $\color{green}+100.00\%$

The above coverage report was generated for the changes in this PR.

[Planeshifter]

Thanks for your work on this PR! Looks great overall, but some changes will be needed for the JavaScript implementation.

In main.js, we need to use the helper function

var float64ToFloat32 = require( '@stdlib/number/float64/base/to-float32' );

in order to ensure that all operations are done in a manner consistent with single-precision arithmetic. Recall that in JavaScript, all numbers are double-precision by default, so to emulate single-precision we must, in addition to using the single-precision variants of math functions, explicitly cast intermediate results and constants to single-precision floats.

[aayush0325]

good morning @Planeshifter! I've wrapped the intermediate results and final answers in float64ToFloat32(). If there's anything else that needs to be changed here please let me know.

[aayush0325]

Also, as mentioned in the questions section of the PR, what should i do about benchmark/c/cephes since it doesn't seem to compile locally and it fails on CI as well. Is there something that I'm missing from my side? (see this commit)