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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Beware: Rep spec on an enumeration type causes code explosion
Date: 1997/12/14
Message-ID: <dewar.882114851@merv>#1/1
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References: <gwinn-0812971210080001@dh5055133.res.ray.com>
 <EKxx9n.Ly1.0.-s@inmet.camb.inmet.com> <348F3238.4487@hso.link.com>
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Date: 1997-12-14T00:00:00+00:00
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Stanley said

<<I find it hard to believe that the efficiency of this
is *implictly* bad.  It seems like the use of holey enum
types for for-loop ranges, array-indexes, etc, would
always default to the use of positions; only placing
the enum value into a location should cause a table
look-up (one index redirection) for the actual value.>>

Well may be you find it hard to believe, but that does not make it false :-)

If you say a(i), where i is of the HET, then the representation of i is
what is stored, and indeed the normal expectation seems to be that the
array i will be indexed by the pos value, thus requiring a rep to pos
conversion, which is the potentially expensive one.

Of course if you say a(red) where red is an enuemration literal of the HET
then there is no additional overhead (or should not be).