Re: Optional Arguments

[tomas]

On Mon, Dec 07, 2020 at 01:37:34PM +0100, pietru@caramail.com wrote:
> 
> 
> > Sent: Monday, December 07, 2020 at 9:16 AM
> > From: "Alexis Roda" <alexis.roda.villalonga@gmail.com>
> > To: pietru@caramail.com
> > Cc: "Help Gnu Emacs" <help-gnu-emacs@gnu.org>
> > Subject: Re: Optional Arguments
> >
> > Hi,
> > 
> > Not sure what your question is.
> 
> It is bit confusing.
> 
> I want to use typh-word-markers to compute ma and mb so I can use the
> two values in another function.  Had put (interactive) in my effort to
> test it, but created problems as you say.  The function would be called
> when cursor is on a word, so that I get the word "beg" and "end".
> 
> (defun typh-word-markers (ma mb)

[...]

As Alexis already said, the parameters in your function aren't probably
doing what you think they do. Consider:

  (setq ma 15)
  (setq mb 26)
  
  (defun foo (ma mb)
    (setq ma 5)
    (setq mb 6)
    (message "ma: %d mb: %d" ma mb))
  
  (foo ma mb)

=> "ma: 5 mb: 6"

  (message "ma: %d mb: %d" ma mb)

=> "ma: 15 mb: 26"

I suspect you are passing the parameters to get their values
"outside" the function. I can only guess that, because you don't
show any context (take this into account to help others help
you :)

But this won't work, because the (setq ...) whithin the function
doesn't "see" the variables outside, but creates variables inside,
initialized to whatever /values/ you pass to the function at call
time.

In other words: what would you expect your function `typh-word-markers'
do do if you call it like so:

  (typh-word-markers 15 16)

...would you expect it to change the number 15 to whatever the word's
beginning position is? You would mess up maths with that :)

Cheers
 - t

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