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From: =?ISO-8859-1?Q?S=E9bastien?= <seb.morand@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Task vs Protected Type
Date: Fri, 30 May 2008 16:09:56 +0000
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>    protected type Semaphore_Protected_Type (N : Natural) is
>       ...
>    private
>       Count : Natural := N;
>    end Semaphore_Protected_Type;

I see, using a discriminant type does not require an initialization. I 
must admit I still have difficulties to think discriminant type while I 
understand quite well how powerful they are.

> Neither. It is a bad idea to use tasks for implementation of low-level
> synchronization primitives (like semaphores). Your web application would
> probably do much more things than just locking. Instead of Wait, you would
> likely have something like Service (Object), which is more like a
> transaction. Because the time required for handling higher level requests
> is sufficiently greater than mere switching contexts, the difference might
> become negligible. At the same time protected objects tend to be too
> low-level. Further, protected actions shall be very short. This requirement
> forces a very heavy design, when you have to do some prologue as a
> protected action, continue work outside it, and complete it again as a
> protected action again. Such things, and semaphore is a typical example of,
> are exposed to various nasty problems.

Ok thanks for the explanations, I understand very well and I'm able to 
make the comparisons with what I'm used to meet in C/C++.

Sebastien