Re: [q-lang-users] Complex numbers

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

John Cowan wrote:
> Albert Graef scripsit:
>>unparse (comp_rect X Y) = '(X+Y*i);
> 
> Sounds excellent to me.  Of course, there would be the risk that
> whatever the pretty-printer produced would not in fact parse
> and evaluate to the same thing, but that's the price you pay
> for sharp tools.

I've implemented this (in cvs now) and it works very nicely indeed. 
Here's a little example (Rob, you should find that interesting, too):

type Rat = private const rat P Q;
public (over) P Q @ (/);
P:Int over Q:Int = rat (P div D) (Q div D) where D = gcd P Q;
unparse (rat P Q) = '(P over Q);

==> 2 over 6 // the result is actually rat 1 3, which is unparsed as:
1 over 3

Note how the `over' operator behaves like a constructor (with equations) 
for Rat objects. The real constructor `rat' is never seen outside the 
module where the type is defined and can thus be hidden by making it 
private. Neat, isn't it? :)

The application to complex.q and rational.q is obvious. But I'm also 
considering equipping the standard container types with unparsing rules, 
e.g., the result of dict [(1,2),(3,4)] would then actually be printed as 
dict [(1,2),(3,4)]. Any objections?

Also, I'm about to turn complex numbers into an algebraic type now. If 
anyone wants to complain, now is your last opportunity. ;-)

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