[CakeML] Adding records to CakeML

[Scott Owens]

There are several possible ways to approach extending the CakeML type system, and several different directions that extensions could go in. I’d be happy to outline some possible projects, but would like to get a sense of your expertise in PL theory and type systems and/or mechanised proof. There are projects suitable for a variety of interests and expertise, but it might be helpful to know before suggesting a concrete approach.

Scott

> On 2016/04/22, at 06:55, Magnus Myreen <magnus.myreen at gmail.com> wrote:
> 
> Hi Francis,
> 
> I'm very happy to hear that you are interested in contributing to
> CakeML. For records and type annotations, Yong Kiam, Scott and Ramana
> are the right people to consult. They should all be on this mailing list.
> 
> I can imagine that records might be a difficult one to start with,
> while type annotations are probably a more gentle introduction.
> 
> There are also some obvious optimisations missing in the compiler. Let
> me know if you are interested in implementing and verifying compiler
> optimisations. Some of the optimisations should be well contained
> within specific intermediate languages.
> 
> Cheers,
> Magnus
> 
> 
> 
> 
> 
> On 21 April 2016 at 22:24, Francis Southern <francis.southern at gmail.com> wrote:
>> Dear CakeML developers,
>> 
>> I want to start by saying that I find your work on CakeML fascinating and
>> I'm eager to find ways to begin contributing, so I'm looking for a small
>> project to get my feet wet with (since I haven't got that much experience
>> with formal development or programming language implementation).  Of course
>> I've seen the list at <https://cakeml.org/projects.html> and I am hopeful I
>> can start working on one of these projects (possibly related to pattern
>> matching) in the near future, but I'm trying to find something smaller that
>> I can make progress on more quickly.  Since I'm working independently at the
>> moment, I suppose I want to get feedback and that buzz of contribution as
>> soon as possible!
>> 
>> So, whilst poking around in the code looking for interesting leads, I came
>> across a list of unimplemented features including records and type
>> annotations in the file documentation/reference.tex.  These seem to me like
>> self-evidently desirable features which are hopefully reasonably simple to
>> implement.  I don't mean to suggest they'll be easy, but they're the easiest
>> meaningful contributions I've been able to identify!
>> 
>> Adding records seemed the more interesting of the two, so I started thinking
>> about it and discussed it a little in the IRC channel.  First off, since I
>> understand CakeML has diverged from Standard ML in other areas, there are
>> choices to be made about the semantics we want (basically, along the lines
>> of SML vs OCaml).  Do we want them to be declared or anonymous?  Do we want
>> unique field names?  Do we want to support field reordering?  Mutable
>> fields?  Subtyping?!  There are probably other possibilities I've either
>> forgotten about or am ignorant of.  The answers to some of these questions
>> also have implications for pattern matching and type inference, of course.
>> 
>> And then there's the implementation.  I think the main decision here is
>> whether we implement records on top of tuples or vice versa.  The
>> implementation will obviously require changes to several parts of the
>> codebase (the type system and inference, the parser, the compiler, etc).
>> This is, of course, the purpose of the whole exercise, but still rather
>> intimidating to me, so any advice on how to approach this (which files would
>> need to be worked on, which could be enlightening to study, etc) would be
>> much appreciated.
>> 
>> In fact, after thinking about all that, I'm wondering if it's actually a
>> better idea to start with type annotations instead!  But anyway, I'm looking
>> forward to hearing your opinions.  I hope that I don't come across as too
>> clueless, and naïve only in the optimistic sense.
>> 
>> Cheers,
>> Francis
>> 
>> P.S.  Thanks to xrchz and YK from the #cakeml IRC channel for the advice and
>> encouragement that led me to write this email.
>> 
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> 
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