Re: What's missing in ELisp that makes people want to use cl-lib?

[Richard Stallman <rms@gnu.org>]

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  > I think these keyword arguments are just like normal elisp
  > optional arguments, they are just passed by name.  So the
  > same problems of writing/explaining them apply.

  > As to whether keyword arguments are intrinsically needed more
  > or less frequently than optional arguments is IMO, very
  > debatable, and entirely dependent on the function.

I think both of these questions are minor issues that threaten to act
as red herrings.  Keyword arguments are better than optional
positional arguments in some circumstances, and the optional positional
arguments are better in some circumstances.

Keyword arguments are better -- sometimes much better -- when one
function accepts many different optional arguments.  There are
functions in Emacs that accept many positional optional arguments, and
some of them would be cleaner if they accepted keyword arguments.

Why don't they?  Because Emacs Lisp doesn't make it easy to accept
keyword arguments.  It is especially a pain in a primitive.  And many
of those functions were defined before Emacs Lisp had such a thing as
a keyword, let alone a keyword argument.

On the other hand, positional optional arguments are better when a
function accepts only one or two of them and they are used often.
They are easier to pass, and easier to remember,

Keyword arguments are easier to use when a function accepts many
different arguments pass.  But this can backfire when it encourages
people to give a function many keyword arguments, on the assumption
that "It doesn't cost us anything to give it more."

It may not cost much more at run time to decode those arguments,
but it costs a lot more to remember what they do, and to use them.

What Common Lisp did to sequence functions was the worst of
everything.  It gave a set of many keyword arguments to functions
which didn't have any, then changed the defaults for those functions
so that one usually needed to pass those keyword arguments,

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)