Re: Invoking a function from a list of functions

[Tim Johnson <tim@akwebsoft.com>]

* Yuri Khan <yurivkhan@gmail.com> [181109 05:28]:
> On Fri, Nov 9, 2018 at 1:03 PM Tim Johnson <tim@akwebsoft.com> wrote:
> 
> > > > Given a list of functions:
> > > > (setq funcs '(scroll-up-line scroll-down-line))
> > > >
> > > > And assuming that these functions have a similar argument list,
> > > > I can invoke a function as:
> > > >
> > > > (funcall (nth 1 funcs))
> > > > ;; or optionally
> > > > (funcall (nth 1 funcs) 2)
> 
> >   What I am interested in is further discussion whether it be from
> >   replies to this topic or more general topics in this area. I'm
> >   restating that I've had a difficult time finding results from
> >   google.
> >
> >     --------------------------------------------------------
> >     That is probably because I don't know the right keywords
> >     or domain-specific terms to use
> >     --------------------------------------------------------
> >
> >   This isn't just difficult for emacs/elisp, I've found it difficult
> >   for python functions invoked from lists or dictionaries. (altho
> >   I've employed such methods for years in python)
> >
> >   If I wished to further research this topic using a search engine
> >   what are the keywords that I might feed to google?
> 
> The term you are looking for is “first-class functions”. This refers
> to passing functions as arguments to other functions, returning
> functions out of functions, storing functions in variables and data
> structures, and otherwise treating functions the same way as other
> values.

  That is exactly correct, yet I find nothing on this topic using 
  “first-class functions” as a keyword/phrase.

 This obscurity is shared by python. The 'list-or-dictionary-of- functions 
 approach that I've used for years in python is just as
 hard to search for. I believe I also used that tactic in C back
 when I did GUI programming, but it has been so very long and I'm so
 very retired ... :)

> A related term, but from object-oriented programming, is “virtual
> method”. This is a narrower concept, that you might want to call
> different implementations of a function depending on the type of its
> argument.
> 

 thanks

-- 
Tim Johnson
http://www.tj49.com