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Newsgroups: comp.lang.ada
Subject: Re: What is wrong with Ada?
From: "Peter C. Chapin" <pchapin@sover.net>
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Date: 12 Apr 2007 19:54:05 GMT
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> But the number of program states is finite, or else the program is wrong
> anyway?

In a Turing complete programming language it is possible to write programs 
with unbounded amount of state. Indeed... this is the essence of Turing 
completeness.

P.S. If I understand SPARK properly, the SPARK subset of Ada is not Turning 
complete because for any given program there is a bound on how much state 
information the program might use. As a result the halting problem is 
decidable for SPARK programs. This is a consequence of the lack of dynamic 
allocation and recursion. Of course useful programs can still be written 
with SPARK despite its theoretical incompleteness. I imagine that making 
SPARK less powerful than a Turing machine is the whole point of the 
restrictions it imposes. Turing machines are hard to analyze.

Peter