Re: elisp question

[Vinicius Jose Latorre]

stan wrote:
> Recently I had cause to go digging into ps-print.el (turned out to be
> version problems in cygwin emacs) and I ran accross something I don't
> understand. For the record I'm not by any means an elisp programmer but
> I can usually at least read the code and do some simple things.
>
> The line I don't think I understand is
>  
> (and (fboundp 'start-process) 0)
>
> Actually that's a fragment of a larger expression. It looks to me like
> this will always be nil. Is this some idiom I haven't seeen or is this
> just a synonym fo nil?
>   

No, this expression returns nil or 0 (zero).

It's evaluated as the 5th parameter (buffer) of call-process-region.

Typing  C-h f call-process-region RET, you can read:

     ......
     If buffer is 0, `call-process-region' returns immediately with 
value nil.
     Otherwise it waits for program to terminate
     and returns a numeric exit status or a signal description string.
     ......