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Re: Using '-1' in a method named '*'
From: |
tomas |
Subject: |
Re: Using '-1' in a method named '*' |
Date: |
Tue, 28 Feb 2017 09:00:30 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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On Mon, Feb 27, 2017 at 08:21:03PM +0100, Andy Wingo wrote:
> Hi,
>
> On Mon 27 Feb 2017 11:06, Alejandro Sanchez <address@hidden> writes:
>
> > (define v (make <vector3> #:x 1))
> >
> > (* -1 v) ; Does not work
> > (* -2 v) ; Works fine
>
> I believe that Guile is doing strength reduction, transforming (* -1 v)
> to (- 0 v).
Woah. This is somehow... exquisite.
> It could be that this is totally the wrong thing. Is (* x 2) -> (+ x x)
> a valid transformation if you don't know the type of x? I don't know.
What we really want to know is the meaning of '*' and '+' (is that akin
to constant folding?), but yes, for that we need some info about the type
of x, I guess.
> I think there's currently an assumption that if you extend *, that you
> will do so in a mathy way, and that you implement - + and similar. But
> in this case it's not the clear right thing to do.
>
> WDYT? We could remove this transformation, or only apply it when type
> inference has run.
If overloading is allowed then yes, it seems type inference has to go
in first?
regards
- -- tomás
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