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let rec and polymorphic functions
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Date: -- (:)
From: Jon Harrop <jon@f...>
Subject: Re: [Caml-list] let rec and polymorphic functions

There are many problems with this. Google for ad-hoc polymorphism, polymorphic 
recursion and generic printing.

On Wednesday 27 June 2007 09:40:31 David Allsopp wrote:
>   out "TEST";

val out : string -> unit

>   out "%d" 0;

val out : format -> int -> unit

As printf is ad-hoc polymorphic, you must supply the format specifier 
immediately and OCaml will generate a custom printer for you. OCaml does not 
use run-time types so you cannot have a generic print function: you must 
specific print functions for each of your (possibly higher-order) types.

Also, recursive calls ossify the function to a monomorphic type, so you cannot 
do polymorphic recursion in OCaml. There are workaround using recursive 
modules or objects but I don't think this is what you want here.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
The OCaml Journal
http://www.ffconsultancy.com/products/ocaml_journal/?e