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NNTP-Posting-Date: Sat, 10 Aug 2013 14:50:30 -0500
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Newsgroups: comp.lang.ada
Subject: Re: 4 beginner's questions on the PL Ada
Date: Sat, 10 Aug 2013 15:50:35 -0400
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Xref: news.eternal-september.org comp.lang.ada:16790
Date: 2013-08-10T15:50:35-04:00
List-Id: <comp.lang.ada>

On Sat, 10 Aug 2013 19:53:41 +0200, Emanuel Berg <embe8573@student.uu.se>
declaimed the following:

>That's Ada, not C. The for loop in C is the for loop in C, and the
>best way to explain it is to say it is excellent for cases where
>the increment variable is usable inside the loop, as in iterating
>an array, *or* when it is known beforehand how many times
>something should be done. Then you post the syntax (the code, the
>example), and - perhaps - mention that 'continue' and 'break' can
>be used to circumvent execution flow. This is the way I would have
>done it. If you would have queried further on the context, and
>dumping URLs to documentation, that's your call.
>

	And that description is rather meaningless to me...

	C-style for loops pretty much mandate breaking apart into parts as they
ARE so generic.

	for ( [initialization part]; 
			[repeat condition part]; 
			[{iteration setup part])
	{
		[action part]
	};

After all, each part is optional!

	for (; [repeat condition part];)
	{
		...
	}

is identical to a while loop

	while ([repeat condition part])
	{
		...
	}

	Heck:

	[initialization part]
	while ([repeat condition part])
	{
		...
		[iteration setup part]
	}

is a full description of the C-style for loop (especially in older C where
you have to predeclare any "loop variables" used in the initialization).

	In Ada, the basic loop, from which all others are built, is:

	loop
		....
	end loop;

>From that one can define loops that iterate over a known/consecutive range
of values

	for counter in first..last loop
		....
	end loop;

Or a loop that has variable number of repeats based upon some condition
determined within the loop itself

	while condition loop
		....
	end loop;

Or even loops that need to repeat some setup actions for each iteration
which affects the exit criteria

	loop
		pre-condition action
		exit when not condition;
		post-condition action
	end loop;

which would require duplicated code in other languages (or misleading loop
structures)

	pre-condition action
	while (condition)
	{
		post-condition action
		pre-condition action /* to set up next iteration */
	}

or

	while (1)	/*	superfluous "condition check", it never exits loop	*/
	{
		pre-condition action
		if (not condition) break;
		post-condition action
	}

or

	for (pre-condition action; condition; pre-condition action)
	{
		post-condition action
	}



>Code is not superficial or lazy. Code *is* programming!

	Code is IMPLEMENTATION...

	Programming takes place outside of any language; one maps algorithms
into the language specific syntax/semantics to implement the algorithm
(program/recipe).
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/