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From: jdege@jdege.visi.com (Jeffrey C. Dege)
Subject: Re: Software landmines (loops)
Date: 1998/09/04
Message-ID: <slrn6uuuko.qcn.jdege@jdege.visi.com>#1/1
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Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada
Date: 1998-09-04T00:00:00+00:00
List-Id: <comp.lang.ada>

On Fri, 04 Sep 1998 05:07:36 GMT, Matthew Heaney <matthew_heaney@acm.org> wrote:
>
>  /* Process a stream of characters.
>   *
>   * The stream is terminated by the value EOF.
>   */
>  for (;;) {
>     Get (C);
>
>     if (C == EOF) break;
>
>     <process C>
>   }
>
>My point is that this is a common kind of problem.  You process a stream
>of items, but one of those items is special, and means "no more items
>follow."  I argue that the formulation above is the most natural way to
>implement this kind of problem.

What are the alternatives?

	Get(C);
	while (C != EOF)
	{
		<process C>
		Get(C)
	}

	while (Get(C), C != EOF)
	{
		<process C>
	}


	goto LABEL5;
	do
	{
		<process C>
	LABEL5:
		Get(C);
	}
	while (C != EOF);

	boolean done = false;
	while (!done)
	{
		Get(C);

		if (C == EOF)
			done = true;
		else
		{
			<process C>
		}
	}

	jump_buf jumpBuffer;
	if (!setjmp(jumpBuffer))
	{
		for (;;)
		{
			Get(C);

			if (C==EOF)
				longjmp(1);
			
			<process C>
		}
	}

>Researchers showed empirically that using the construction above,
>programmers produced fewer errors:
>
>Cognitive Strategies and Looping Constructs: An Empirical Study
>Soloway, Bonar, Ehrlich
>CACM, Nov 83, Vol 26, No 11, p853-860
>
>As they say, the proof is in the pudding, not the pudding recipe.
>

-- 
"Necessity is the mother of invention" is a silly proverb.  "Necessity
is the mother of futile dodges" is much nearer the truth.
		-- Alfred North Whitehead