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NNTP-Posting-Date: Thu, 01 Sep 2005 17:56:22 -0500
From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: Surprise in array concatenation
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Date: Thu, 01 Sep 2005 17:56:22 -0500
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Date: 2005-09-01T17:56:22-05:00
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>I completely agree with the marginal utility of other-than-1 least
>array indices.
   I strongly disagree.  While not dirt common, other 'firsts in
declarations do occur.  -n ..  +n comes to mind.  If you are going to
handle slices, you have to assume 'first /= 1 anyway, so you're not losing
much by allowing it in declarations.  Using 'first instead of 1 also makes
it simple to change between integer and enumeration value indexes.  The
way Ada.Text_IO.Get_Line (et al) returns Last, which works even if you
passed it a slice, has surely prevented many an error as compared to other
languages which would likely return a count (since "all arrays start at
x") and depend on the programmer to do any arithmetic needed to turn it
into an index.  And if you started all arrays at 1, you probably wouldn't
allow the idiom
  subtype cards is string(1 .. 80);
  subtype sequence is range 73 .. 80;
  ...
  if card(sequence) = (sequence=>' ') then