Re: [Chicken-users] Imlib2 question

[Peter Bex]

On Mon, Sep 24, 2007 at 04:29:25PM -0400, William Ramsay wrote:
> That's the problem, I don't know what to use.    I've tried call-with-values
> and receive, but both give me errors, mostly because I have no idea what
> I'm doing.    Receive expects  (name1 name2 ...) valexp body, but this
> produces an error since name1 is not a command.
> 
> Why not just return a list and make it simple?

Because the pixel routines conceptually return four values, _not_ one value
which is a list.

> The call to (imlib:pixel img x y) should return the  r, g, b, a  values 
> of the pixel. 

It should, and it does.

> Just calling it produces r.

Yes, this is (afaik) a deviation from the standard.  I don't like
it one bit, precisely for this reason: it's damned confusing.  I want
an error if I forgot to receive all values, I don't want the first
value, dammit!

(that's what it does; it discards all values except the first)

Complain to Felix about this if you don't like it :)

> The others are there, but how do I get them?

(receive (r g b a)
    (imlib:pixel/rgba img x y)
  (do-something-with r g b a))

Alternatively,

(call-with-values (lambda () (imlib:pixel/rgba img x y)) (lambda (r g b a) ...))

> confused....

Hope this helps!

Cheers,
Peter
-- 
http://sjamaan.ath.cx
--
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