From: drw@cullvax.UUCP (Dale Worley)
Subject: Re: The AFT Attribute
Date: Mon, 22-Sep-86 16:38:18 EDT [thread overview]
Date: Mon Sep 22 16:38:18 1986
Message-ID: <350@cullvax.UUCP> (raw)
In-Reply-To: 12239247219.20.MENDAL@Sierra.Stanford.EDU
> I'm confused again. In the LRM, 3.5.10(9) states (parenthetically)
> that the value of the AFT attribute is the smallest positive N
> such that (10 ** N) * T'DELTA >= 1.0. Now, 3.5.10(15) states that
> the value returned by AFT depends only on T'DELTA. [3.5.10(15) is
> a "note".]
>
> Can these two paragraphs imply a cohesive semantics for the AFT
> attribute? Using 3.5.10(9) on the following type:
>
> type Fix is delta 1.0 / 16.0 range 0.0 .. 1.0;
>
> The smallest value N that satisfies the equation is 2. But how can
> one represent 1.0 / 16.0 accurately in two decimal digits?
> [1.0 / 16.0 = 0.0625]
>
> What am I missing here?
The point is that T'AFT digits is not guaranteed to be enough to
represent the values of type T. (Consider
type Fix is delta 1.0 / 3.0 range 0.0 .. 1.0;
No number of digits is sufficient!) All you are guaranteed is that
the delta is >= (10 ** -T'AFT).
Now, what 'AFT is good for, I don't rightly know... Any guesses,
campers?
Dale
next prev parent reply other threads:[~1986-09-22 20:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
1986-09-16 0:32 The AFT Attribute Geoff Mendal
1986-09-22 20:38 ` Dale Worley [this message]
1986-09-24 5:11 ` Doug Bryan
[not found] <20@<12239247219>
1986-09-22 12:44 ` stt
1986-09-24 15:13 ` stt
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