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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: type declaration and storage requirements
Date: 04 Jun 2002 11:35:40 +0100
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Date: 2002-06-04T11:35:40+01:00
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18k11tm001@sneakemail.com (Russ) writes:

> Suppose I have a particular range in mind, and I just want to get
> the maximum number of digits I can get for, say, a 32-bit word. Is
> there a simple way to determine how many digits to specify? If I
> specify one digit too many, can it step the storage requirement from
> one to two words? I'm no expert, but it seems to me that what you
> really want to be able to specify is not the number of digits but
> rather the total number of bytes to be used.

If your requirement is to specify a size for the values, say

  type My_Short_Float_Type is new Float;
  type My_Long_Float_Type is new Long_Float;

or

  subtype My_Short_Float_Type is Float;
  subtype My_Long_Float_Type is Long_Float;

which are pretty likely to map to C float and double.

If on the other hand your requirement is to specify the precision your
algorithm requires, you really do need

  type My_Float_Type is digits 7;

and if it turns out that that needs 8 bytes (ie double), so be it.