stanc3 online demo for pedantic mode, canonicalizer, auto format, etc

[rok-cesnovar]

Given that we build a javascript version of stanc3 with each release, it would be very simple to make a static web page hosted on github that would enable demos of pedantic mode, canonicalizer (--print-canonical) and other options like that. The "compiling/transpiling/formatting/...." steps are done on the users end.

If we make Github Pages for this repository, that could be hosted under https://mc-stan.org/stanc3/demo

It probably does not make sense to add printing of C++.

Any thoughts?

[wds15]

Cool !!!

EDIT: It would be great to make this thing Stan version specific. So this thing should have a switch which allows to use different versions of the Stan transpiler for this. That is useful to make it easy for people to use older Stan versions and ensure that their Stan program runs with a certain Stan version.

[bob-carpenter]

Sounds cool.

I think printing the C++ would also be useful.

Does GitHub let you host servers or would you be plumbing in other servers?

[rok-cesnovar]

This would use github pages like we do for hosting the website. Given that its only html and a javascript file its a static page that github can handle.

[rok-cesnovar]

There is now a prototype available: https://rok-cesnovar.github.io/stanc3js-demo/index.html

It lacks any CSS styling to make it prettier but it can:

• print C++
• do a pedantic check
• list supported signatures
• run auto formatter and canonicalizer
• show how stanc3 optimization changes the C++

[WardBrian]

I think especially with #894 merged, it would be really cool to put this somewhere more official. It reminds me a lot of stuff like https://try.ocamlpro.com/

[rok-cesnovar]

Yeah, we could probably place it somewhere like mc-stan.org/stanc3-try or -demo or something like that. Still need to pretty-up the interface, havent touched this in a while.

[WardBrian]

I was impressed that it had kept up to date the whole time, but (of course!) it's just pulling the nightly stanjs from Github

[rok-cesnovar]

I finally got back to fixing this. The link again https://rok-cesnovar.github.io/stanc3js-demo/

Fixes:

• supports the new style of signatures so that the function search now works, as does linking to a specific function: https://rok-cesnovar.github.io/stanc3js-demo/signatures.html?function=fabs
• fixed pedantic check (previously it looked for stderr, it now looks for out.warnings)
• a bit nicer interface but not really :)

TODO:

• add Stan syntax highlighting (this should be solved whenever we solve it for @spinkney's helpful Stan functions repo, I think with highlight.js?)
• link to Stan docs from the signatures subpage
• support modular canonicalizer (after Modular canonicalizer #1058 )
• add option of selecting older versions

Other than that I think we can start discussing if we want this on the official Stan page and where. Maybe a topic for the Stan weekly meeting.

[spinkney]

I think you can use highlight.js, prism.js, or rouge. There are issues/prs in each of these to update Stan syntax:

• highlight.js issue #3410
• prismjs issue #3236
• rouge issue #1768
  • rouge pr #1735

Can't wait for the modular canonicalizer as well!

Is it possible for the optimizer to output stan code? As in, what should the Stan code have been written to generate the optimized c++ code? It would be a nice teaching tool.

[spinkney]

As I was typing that there is already a pr in prismjs! PrismJS/prism#3238

[rok-cesnovar]

A web canonicalizer would also come in handy for users to easily update their models when they start seeing deprecation warnings (particularly the array syntax one for example).

[WardBrian]

I think it would also be useful to let users select a version of the compiler to use if possible. Make it easy to compare codegen or use an older version (especially bc after a deprecation is 100% removed, it won’t be able to be canonicalized)

[WardBrian]

@spinkney make sure that the 3i syntax for complex literals is included in these PRs/issues, it currently highlights it very poorly in most cases