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Re: [Chicken-users] Minor problem with args egg


From: Peter Bex
Subject: Re: [Chicken-users] Minor problem with args egg
Date: Wed, 13 May 2015 11:52:37 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, May 13, 2015 at 03:38:41AM -0600, Matt Gushee wrote:
> Anyway, it seems that if you specify an option with no arguments, e.g.
> 
>    (args:make-option (v version) #:none
>                               "Display compiled versions.")
> 
> ... then when the user invokes the program with that option, you get:
> 
>    '((v . #f) (version . #f))
> 
> ... which means that alist-ref will not tell you whether the user passed
> that option, or it simply isn't present. I wonder if it wouldn't be better
> for a no-arg option to produce a symbol, #:undefined perhaps?

I would expect #t to be present if the user passed the option.  This
allows for easy presence-checking, and it's similar to an option that
accepts "yes" or "no".

Cheers,
Peter

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