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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Hash Type Size
Date: Mon, 19 Aug 2013 17:21:52 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2013-08-19T17:21:52-05:00
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"AdaMagica" <christ-usch.grein@t-online.de> wrote in message 
news:8e573dcd-e84d-423b-b319-d2224a1ce9ae@googlegroups.com...
> On Sunday, August 18, 2013 11:05:47 PM UTC+2, sbelm...@gmail.com wrote:
>> What is the size of Ada.Containers.Hash_Type intended to be?  ...  Is the 
>> intent that Hash_Type should be the native size of the machine (and the 
>> implementation is wrong/advice is vague), or that it actually should be 
>> 32-bit if possible?
>
> See AARM A.18.1(8.b/2). Looks like ist should be the native size. But it's 
> only advice.

My recollection is that we said that with the intent that we didn't want it 
to be smaller than 32-bits unless there was a good reason (like no 32-bit 
math on the target). I don't think there was any intent to suggest that it 
ought to be larger (it's not practical to store more than 2**32 items in an 
Ada container).

There's not much point anyway; you can't directly hash 32-bit signed 
integers in a 32-bit hash value without resorting to Unchecked_Conversion, 
and then you've already completely left the realm of safe and portable 
(neither Integer nor Hash_Type has a defined size by the RM).

                                                          Randy.