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From: "Peter C. Chapin" <pcc482719@gmail.com>
Subject: Re: Inferring array index type from array object
Newsgroups: comp.lang.ada
Date: Wed, 23 Jun 2010 10:27:46 -0400
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Date: 2010-06-23T10:27:46-04:00
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Niklas Holsti wrote:

> I don't think such large language changes would be necessary. The 
> expression S'Range gives the compiler all the information about the type 
> and its constraints, so I see no reason why Ada could not be extended 
> simply to allow S'Range in a variable declaration, as in the above 
> quoted "I : S'Range". The declared variable "I" would have the same 
> (sub)type as the loop counter in "for I in S'Range loop ...".

This seems weird to me. S'Range is a range, not a type. I agree that it
includes type information, but then so does an object.

X : Integer;
Y : X;       -- Let Y have the same type as X. Weird.

Type inference is a big subject and while it can be very nice in languages
that support it comprehensively, type inference doesn't really seem like
the "Ada way" to me. In any case, once you start supporting type inference in
any form you have to wonder just how far down that road you want to go. Right
now Ada only infers types in one very limited case (right?)... that is in
support of implicitly declared loop index variables.

Peter