Re: [Caml-list] Observations on OCaml vs. Haskell

[Danny Yoo <dyoo@hkn.eecs.berkeley.edu>]

> > I've written several functions that can work with a "number-like"
> > type.  I don't really care if I get an integer, Int32, Int64, float,
> > or what But since these are all different types in OCaml, I am forced
> > to care, right down to using +, +., or Int64.add to perform basic
> > arithmetic.

[text cut]

> However, I do agree with you that the mess with OCaml having to add
> totally different operators to do arithmetic for integral and floating
> point types is a wart in what is otherwise an elegant language.  The
> compiler could very easily make the arithmetic operators polymorphic,
> and constrain the operands to be of the same (numeric) type, and signal
> an error if you attempt to, say, multiply an integer with a floating
> point number without doing the proper conversion.


The comparison operators '<' are polymorphic, but that does incur some
performance cost.  Richard Jones's wonderful tutorial on OCaml touches on
this under "Polymorphic types":

    http://www.merjis.com/developers/ocaml_tutorial/ch11


He shows that:

;;;
let max a b =
    if a > b then a else b
in
    print_int (max 2 3)
;;;


uses the polymorphic version of '>', even though the use of max here uses
only ints.  I think OCaml's arithmetic operators are monomophic to avoid
the cost of polymorphism.



> Unless there's something in the design of the type system that prevents
> this from happening except at run-time...?

I wonder if the Cartesian Product Algorithm might be applicable to OCaml.
There's a paper about it here:

    http://research.sun.com/self/papers/cpa.html


where it sounds like it might be able to attack this problem.  I'd love to
be able to use just one '+' operator, rather than remember '+' vs '+.' vs
'+/'.  *grin*

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