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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: SPARK - Bubble Sort on Rosetta Code
Date: Thu, 26 Aug 2010 23:32:08 +0100
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Date: 2010-08-26T23:32:08+01:00
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Phil Thornley <phil.jpthornley@gmail.com> writes:

> I've put some SPARK code for the Bubble Sort task on Rosetta Code and
> I would welcome opinions on whether they make a good showcase for
> SPARK

It took me a while to find them -- at
http://rosettacode.org/wiki/Sorting_algorithms/Bubble_sort#SPARK.

> The first is simply shown to be type-safe.

Is this the same as "guaranteed free of any run-time error"?

What would non-SPARK code do to make it fail?

> The second, with identical Ada code, proves that the output array is
> sorted.

Are zero-length arrays forbidden in SPARK? I ask because of 

      --# check A'Last <= A'First -> A'Last = A'First;

(what's that -> ? I understood that the syntax was
   'check <boolean expression>').