Re: [q-lang-users] Polynomial module.

[Albert G. <Dr....@t-...>]

Keith Trenton wrote:
> - sieve {X|Xs} = {X|var Y : sieve {Y:Y in Xs,Y mod X<>0}};
> 
> [1] one advantage wrt. in-ining "var Y : " : only one (1) line of code is required (see above);

The other advantage is that the scope of the variable(s) would be
restricted just to a single expression instead of the entire rule.

> [2] one (possible) disadvantage wrt. in-ining "var Y : " : are we overloading the colon <:> in an ambiguous way?

I don't think so. The "var" should disambiguate it.

> [a] sieve {X|Xs} = {X|local Y : sieve {Y:Y in Xs,Y mod X<>0}};

We already have the "var" keyword so why not use it?

> [b] sieve {X|Xs} = {X|var Y in sieve {Y:Y in Xs,Y mod X<>0}};

"in" doesn't work, it can't be a predefined keyword, because it's
declared as a user-defined operator in the standard library. That's why
I picked the colon instead.

> [d] sieve {X|Xs} = {X|Y| sieve {Y:Y in Xs,Y mod X<>0}};

This looks nice but introduces syntactic ambiguities because | is also
used in the list/stream syntax. E.g., consider {X|bla X}. Is that a
stream with head X and tail bla X or a single-element stream with a var
declaration in it?

Cheers,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag