]>
> Andrew Kay <akay@sharp.co.uk> wrote, in the caml-list archives:
> > We are in the process of converting our Caml code into OCaml, and
> > have a problem choosing an infix syntax for function composition
> > [...] What do other OCaml people use for function composition? Is
> > there standard emerging?
>
> I found no answer in the archives, so I'd like to raise the same
> question again: is there a consensus for choice of infix composition
> operator? Failing that, is there some design principle that warranted
> its omission?
>
> Thanks,
> John Whitley
The normal infix operator should be a o, or more precisely a $\circ$
symbol. Unfortunately if we add o in the syntax of Caml, this will be
a bit strange to have this identifier as an infix operation (moreover
this implies difficult to explain syntax errors in programs).
In fact we discourage the usage of functional composition as a general
programming tool, since:
-- it only save a few characters in programs
(Compare
let h = f o g
with
let h x = f (g x);;)
-- it breaks the polymorphism
(if defined as
let h = f o g
h is not generalized, since its definition is a function
application, whereas inline expansion of functional composition
let h x = f (g x)
being the definition of a function is properly generalized.)
-- it is not so clear, especially in case of composition of curried
functions
(Consider
let f x y z = x + y + z
then the compositions
f o (f 2 3)
or (f 1) o (f 2 3))
It is still possible to define a composition operator to use in
trivial cases. So you may choose any multi-character infix operator
such as ++, if you really need functional composition.
Best regards,
Pierre Weis
INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://cristal.inria.fr/~weis/