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Re: A few questions regarding markup

From: David Kastrup
Subject: Re: A few questions regarding markup
Date: Sun, 15 Nov 2009 21:06:34 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux)

Reinhold Kainhofer <address@hidden> writes:

> Am Sonntag, 15. November 2009 20:16:51 schrieb Nicolas Sceaux:
>> Le 14 nov. 2009 à 09:29, David Kastrup a écrit :
>> > Now the harp-pedal command defines the property signature
>> >
>> >  ((size 1.0)
>> >   (harp-pedal-details)
>> >   (thickness 0.5))
>> >
>> > So far, so fine.  It
>> > then calls make-harp-pedal without passing it those let-bound
>> > variables.  As far as I understand Scheme and its closures, this means
>> > that the defaults specified in this manner are ignored.
> I wrote that code, and I have to admit that I don't understand this part at 
> all. I simply copied code from somewhere else and tweaked it so that it 
> worked....
>> > make-harp-pedal then starts off with
>> >
>> >  (let* ((size (chain-assoc-get 'size props 1.2))
>> >        (details (chain-assoc-get 'harp-pedal-details props '()))
>> Just remove the useless binding of `size' in the let form,
>> and give the appropriate default in the property argument.
> Ah, interesting... So, in the make-harp-pedal function, the properties
> defined in the harp-pedal markup function are available?

Not if make-harp-pedal is not defined in the scope of the harp-pedal
markup function.  If I understand Scheme correctly.  size is
automatically let-bound to the correct value (default if not specified
in properties) within the markup function defined with

> That's cool!

Yes and no: the coolness does not inherit into called functions.  My
personal preference with the harp pedals would be to throw out
make-harp-pedal altogether (it is just used as a shared helper function
for an outcommented different definition which should likely just get
removed altogether).

But I think I covered most issues in my first post anyway.

David Kastrup

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