q-lang-users

[q-lang-users] Infixed Ternary Operators?

[Rob H. <hub...@gm...>]

Dear Albert,

I think the answer to this question will be "no", but I thought I'd ask 
it anyway (just in case).

It is possible to define a ternary infix operator? For example, suppose 
the operator is called f, and takes three arguments
    public f P X Y;

I'd like to write
    X (f 13) Y
rather than
    f 13 X Y

In other words, I'd like the partial application
    f 13
to yield a ('specialised') infix operator.

If it can't be done, then I don't consider it important enough (or even 
necessarily desirable) to implement. I just wondered whether there might 
be some kind of Q trick I'd not thought of.

Thanks,
Rob.

Re: [q-lang-users] Infixed Ternary Operators?

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

Hi Rob,

> It is possible to define a ternary infix operator? For example, suppose 
> the operator is called f, and takes three arguments
>     public f P X Y;
> 
> I'd like to write
>     X (f 13) Y
> rather than
>     f 13 X Y

No, sorry, this isn't possible right now. Since operators are detected
at the lexical level already, I don't even see how this could be
implemented in an LALR(1) parser.

I think there are a few languages which essentially open up the language
syntax to allow the programmer to do this kind of thing (define new
mixfix operators etc.), but I don't think that this would work well in
modern FPL syntax with curried function applications.

> If it can't be done, then I don't consider it important enough (or even 
> necessarily desirable) to implement. I just wondered whether there might 
> be some kind of Q trick I'd not thought of.

Well, you could define an ordinary infix operator, but then you'd have
to use something like X f 13 Y which would actually be parsed as X f (13
Y) so this is probably not what you want. It would be a rather dirty
trick anyway, and wouldn't work in all cases (e.g., X f succ 12 ==> X f 13).

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