In matrix_exp_pade, rename return variable pade_approximation, and de…

[charlesm93]

Submisison Checklist

• Run unit tests: ./runTests.py test/unit (Ran 9 tests for matrix exponential).
• Run cpplint: make cpplint
• Declare copyright holder and open-source license: see below

Summary:

In stan/math/prim/mat/fun/matrix_exp_pade.hpp, rename return variable pade_approximation, and declare variable right before it gets used, as oppose to at the top of the function.

See issue #456

Intended Effect:

• Code readability
• Memory isn't allocated for a variable that only get's used later
• Aesthetics

How to Verify:

The first two intended effects are trivial. Code doesn't break.
The question of aesthetics is considerably more complicated and profound. What is beauty, and more importantly what is it in the framework of Stan, where only computer scientists seem to grasp it?

Side Effects:

None.

Documentation:

None.

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Metrum Research Group LLC

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[syclik]

Looks good to me.

[syclik]

The question of aesthetics is considerably more complicated and profound. What is beauty, and more importantly what is it in the framework of Stan, where only computer scientists seem to grasp it?

For aesthetics, we've gone with Google's style guide with a few modifications:

• Google Style Guide: https://google.github.io/styleguide/cppguide.html
• Stan's itemized exceptions to the Google Style Guide: https://github.com/stan-dev/stan/wiki/Coding-Style-and-Idioms

I can't directly answer your deeper question, but I think the concept you're missing is that code is read more often than written. Thought and care needs to be put into constructing it so it can be revisited in the future. Imagine yourself having to read and understand your code in the future: not only what it does (code never lies), but the intent. It's not necessarily about beauty, but about function. It's a lot easier to practice by reviewing code that's not written by you. If you have time, review the open pull requests.

[charlesm93]

I didn't mean to undermine the importance of abiding to coding standards. I've actually spent a lot of hours last week cleaning up Torsten to make it more readable for future coders and easier to edit. I'll definately look through the links you posted and some open pull-requests.

[syclik]

:). It wasn't interpreted that way.

I was just trying to get to someplace where I could help answer your question. It's tough writing things for public consumption. You have to be in a different mindset.