Probability Distribution and Statistical Functions -- Exponential Distribution Module

[Jim-215-Fisher]

This is the second round of probability distribution and statistical functions, continuing from #240. Since the whole modular structure has been changed, each distribution will have its own PR.
This PR contains exponential distributions. Files uploaded are:
src/stdlib_stats_distribtuion_exponential.fypp
src/CMakeLists.txt
src/Makefile.manual
src/tests/test_distribution_exponential.f90
src/tests/CMakeLists.txt
src/tests/Makefile.manual
doc/specs/stdlib_stats_distribution_exponential.md
doc/specs/index.md

[Jim-215-Fisher]

@jvdp1 Accidental delete, please help.

[jvdp1]

@Jim-215-Fisher For some reasons you also deleted the branch Distribution-Exponential, and so, we cannot reopen this PR.
However, the branch seems to still exist in your repo. So, I suggest to reopen a new PR for this module.

[awvwgk]

You can always recover the branch, however we might not be able to reopen this PR. Unless you haven't done so yet use the following the commands to recover the latest state of this branch:

git fetch [email protected]:fortran-lang/stdlib ff0da265f5fcf285ce04e15a09625edaefecf51c
git checkout FETCH_HEAD
git switch -c Distribution-Exponential
git push [email protected]:Jim-215-Fisher/stdlib Distribution-Exponential

[jvdp1]

I checked @Jim-215-Fisher repo and it seems that there is a branch called Distribution-eponential, with this last commit: 212bc33dd7b1f43a59a8d904c6a17a1e4aae3eab called "convert expon name to exp and some words change" which does not seem to have been psuhed in this PR.

Therefore, I suggest to follow @awvwgk procedure. However, I would give it anoter name (e.g., Distribution-Expornential-1) and then to merge both branches if they diverge, to be sure you don't loose something.

[Jim-215-Fisher]

This branch has been updated. All the corrections have been made.

[gareth-nx]

LGTM, thanks

[jvdp1]

In general LGTM. Only a few minor comments. Thank you for this work.

[gareth-nx]

Suggest to finish with "and has the same type as lambda."

[gareth-nx]

Thanks, I noticed a few very minor details in the documentation, and continue to approve merging this.

[jvdp1]

Thank you for this PR @Jim-215-Fisher . Currently I have no additional comments.

[gareth-nx]

@jvdp1 @epagone @Jim-215-Fisher Does anyone object if we merge this now?

[jvdp1]

@jvdp1 @epagone @Jim-215-Fisher Does anyone object if we merge this now?

Good for me!

[epagone]

No objections from me as well!

Edit: just realised that has been merged already 👍 Thanks @Jim-215-Fisher and all reviewers!