RE: [Caml-list] Future of labels

[Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>]

From: "Mattias Waldau" <mattias.waldau@abc.se>

> Could you plz post a good argument for commuting labels.
> 
> Even if we have optional arguments, we could require that the
> arguments should be given in the correct order, and that
> optionals may be skipped.

Should I understand this as support for the classic mode ?
This is exactly what it allows/requires.
In fact it also allows commutation between optional arguments,
which I believe is not only useful but necessary, when you think that
some library functions have more than 10 optional arguments, and
nobody wants to remember their order. Compare with the pain they are
in emacs lisp.

Commuting for non-optional arguments is another problem.

I'm not sure I can give very convincing arguments, except for
functions that have more than 5 parameters, and were again you don't
want to remember their order. To be more precise, order alone is not
enough to remember the role of the arguments, and you probably don't
want to have to remember both name and order: one should be enough.

Since most functions have less than 5 non-optional arguments, this is
mostly a question of taste. I program always in this style, very often
permuting parameters in functionals. One specific advantage is with
respect to partial application: when defining a function you don't
have to carefuly design the parameter order to allow many partial
applications, since you can partially apply in any order.
If you want to have an idea of what it looks like, see the sources for
ocamlbrowser in otherlibs/labltk/browser. This is not very refined
code, but it uses commutation a lot.

Last, the concept of having everything commute is neat. Once you've
started to put enough labels, you really don't have to care about
parameter order anymore, at all.

Does this answer you question ?

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Jacques Garrigue      Kyoto University     garrigue at kurims.kyoto-u.ac.jp
		<A HREF=http://wwwfun.kurims.kyoto-u.ac.jp/~garrigue/>JG</A>
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