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[Caml-list] Default values for structures (feature request)
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Date: 2004-06-02 (12:12)
From: Richard Jones <rich@a...>
Subject: [Caml-list] Default values for structures (feature request)

Could have a syntax for default values for structures?  Something

type t = { field1 : int = 0;
           field2 : string;  (* no default *)

It's sort of possible to do this currently for non-mutable structures
by having a default_value declared, and writing:

let new_value = { default_value with field2 = "new string" }

but this doesn't allow the module to force the user to declare certain
fields in a new value.

The reason for having default fields is so that I can export struct-
ures from my module interface, but be able to add fields with default
values later without breaking dependent code.  (But in some circum-
stances I would deliberately add fields without default values in
order to break code).


Richard Jones. http://www.annexia.org/ http://www.j-london.com/
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