[m-dev.] fact tables

[Fergus Henderson]

David Matthew OVERTON, you wrote:
> Fergus Henderson wrote:
> > 
> > Currently fact tables
> > (1) support only the types `int', `float', and `string'
> > and (2) are not documented (some documentation was mailed to the
> > mercury-developers mailing list, but was never committed).
> > 
> > A solution to (1) is not likely in the near future.
> > 
> > Given this, we have several options:
> > 	(a) document them
> > 	(b) add documentation for them to the .texi files, but leave
> > 	    it commented out, until such time as (2) is solved
> > 	(c) delete the support for fact tables
> > 
> > Opinions?
>
> I don't think the support for fact tables should be removed from the
> compiler.  They can be useful even though they currently support only
> a few different types (I've used them for a couple of different things
> and I believe Tom has too).  Also, they don't interfere with the
> operation of any other part of the compiler.

Well, like almost any feature, they do make maintenance more difficult.
For example, if we were to retarget the Mercury back-end to produce
Java or C-- instead of C, we would have to significantly modify
fact_table.m.

> I still have the .texi documentation I wrote.

Yes, so do I, thanks to the mercury-developers list archive.

> As for whether the documentation should be commented out or not, I
> suppose it doesn't look very good to include visible documentation for
> an unfinished feature.  But, given that the current implementation is
> already useful for a wide variety of situations it might be a good
> idea to let people know about it.

... so that they can write code which will break when they try to
port it to future implementations that don't support it :-(

Nevertheless the concensus seems to be in favour of retaining and
documenting fact_table.m, so that is what I'll do.
I'll add the documentation to the reference manual as Zoltan suggested.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3         |     -- the last words of T. S. Garp.