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Message from discussion Odd length keyword list
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Matus Kmit  
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 More options Jan 12 2012, 3:19 am
Newsgroups: comp.lang.lisp
From: Matus Kmit <simply.nit...@gmail.com>
Date: Thu, 12 Jan 2012 00:19:21 -0800 (PST)
Local: Thurs, Jan 12 2012 3:19 am
Subject: Re: Odd length keyword list
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On 11 Jan., 18:59, kenny <kentil...@gmail.com> wrote:

> On Jan 11, 10:45 am, Matus Kmit <simply.nit...@gmail.com> wrote:

> > Hi

> > I have this macro:

> > (defmacro format-time (one &optional two &key format-fn)
> >   (let ((one* (eval one))
> >         (two* (eval two)))
> >     (if two*
> >         `(,format-fn t "(~a:~a - ~a:~a)" ,@one* ,@two*)
> >         `(,format-fn t "~a:~a" ,@one*))))

> > If I try to macroexpand it with (macroexpand '(format-time (normalize-
> > consed-time '(1 . 2)) :format-fn format)) I am getting the following
> > error:

> > Odd length keyword list: (FORMAT)
> >    [Condition of type CCL::SIMPLE-PROGRAM-ERROR]

> > What is wrong?

> Answered elsewhere, I presume. Meanwhile, you are pretty much doomed
> trying to make mix optional and keyword params. But macros give you a
> little more control, so you might have done:

>   (defmacro format-time ((one &optional two) &key (format-fn 'format))

> I threw in the default value for format-fn, which you really should
> have.

Thanks all for your help. I got it.

> Supermeanwhile: why is this a macro?

> -hk

More or less an experiment, while being bored at work and messing
aroung with lisp trying to understand macros, eval, parameter types,
etc...

On the other hand I was looking for a way how to splice parameters
which are given in a list inside the format function. The first thing
I could think of was macro, although a syntactic abstraction for this
particular case probably does not make much sense. Meanwhile :-), I
remembered "apply", which seems to do just fine what i need:

(apply #'format t (cons "~a:~a" (normalize-consed-time '(1 . 2))))

greetings,
Matus


 
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