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Date: Sat, 30 Aug 2008 12:59:04 +0200
From: Damien Carbonne <damien.carbonne@free.fr>
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Subject: Re: Very confused by Ada tasking, can not explain the execution
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Date: 2008-08-30T12:59:04+02:00
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climber.cui@gmail.com a �crit :
> Thank you Jim for modifying the program and making it work. I saw how
> you modify the guarding conditions for the procedures. In fact, the
> conditions are fine by themselves, because i wrote the same program in
> Java. However, the modified program is working now. It indeed reminds
> me that Ada probably follows the 'strict evaluation' rule when it
> comes to the boolean expressions, so in
>   if Next=1 and State=0 and D<N and Needs(D)  then ...
>   Ada probably would evaluate all the predicates connect by logical
> AND, but as soon as D=N is reached, array index for Needs(_) would go
> out of bound (because Needs is defined to be  array(0..N-1) of
> boolean). I am just guessing here.

Use "and then" instead of "and" to obtain what Java does with "and" :
--> if Next=1 and then State=0 and then D<N and then Needs(D)  then ...

> 
> This would not cause exceptions in Java, because java follows the non-
> strict evaluation rule.
> 
> tony