Implement expit

[MatthewCochrane]

Resolves #27 .

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Description

What is the purpose of this pull request?

This pull request:

• Implements the expit function.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves RFC: add the inverse logit function #27

Questions

Any questions for reviewers of this pull request?

No.

Other

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Ended up using 1.5 * EPS for the tests as discussed in the gitter chat.

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@stdlib-js/reviewers

[kgryte]

@MatthewCochrane Wow! This PR looks great. Just some minor documentation changes and a possible benchmark bug. Once resolved, this should be ready for merge! Thanks for working on this!

[MatthewCochrane]

Thanks for the feedback. I've made the changes you requested and fixed that benchmarking bug. I haven't actually run the c code. I suppose i need to make install deps to get boost to be able to compile it? What's the purpose of the benchmarks in other languages by the way? I take it to compare with our javascript implementation? But there is no automated way to run the other language benchmarks yet?

[kgryte]

@MatthewCochrane To run C benchmarks,

$ make benchmark-c BENCHMARKS_FILTER=.*/expit/.*

In order to run these C benchmarks, you do not need to install Boost. You only need Boost to run benchmarks against Boost, which the C benchmarks in this PR does not use.

Note: in order to compile C benchmarks, you will need gcc installed, which, if you are not on Windows, should not be required.

And you are correct. The benchmarks in the other languages are included in order to compare implementations to (1) reference implementations and (2) baseline performance implementations. In this case, including a C benchmark is useful for establishing baseline performance and assessing how much a JavaScript implementation deviates from the baseline.

[MatthewCochrane]

Ahh great. Good to know, thanks. Yep, makes sense.

[kgryte]

@MatthewCochrane No problem! Taking a final look at the PR now!