Re: [q-lang-users] New stuff in cvs: multichar ops, views

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

John Cowan wrote:
> I always forget that -2 is the application of minus to 2 rather than a
> constant, so I write things like "foo -2", which then turns out to be
> "(foo -) 2".

Well, syntactically the '-' in '-2' is a unary minus, although
semantically, it's still a number and not an explicit application of
minus. IMHO, that's the only reasonable way to implement it, since I
want '-2' and '-X' to be parsed in the same manner.

>> As a first exercise, I just comitted some changes which turn Complex
>> into an ADT with the virtual constructor (:+). So the constant i now
>> prints as 0:+1.
> 
> I don't like that much.  I suppose there is no way to make 0+1*i the
> constructor/view?  I guess not, since Q is eager.

Well, X+Y*i doesn't work here since '+' is not a virtual constructor of
Complex, so while you can use this for pretty-printing (as we did in Q
7.6), you can't write stuff like 'foo (X+Y*i) = ...'. So, to make
matching against the view work, the head symbol of the view must be a
virtual constructor of the type and that's the purpose that ':+' serves.
We could have something like 'X:+Y*i' instead of just 'X:+Y' but that
seems redundant.

What's so bad about 'X:+Y'? I can easily read ':+' aloud as "+i times".

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