Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!sm.unisys.com!csun!csuna!abcscnuk
From: abcscnuk@csuna.UUCP (Naoto Kimura)
Newsgroups: comp.lang.pascal
Subject: Control variables in FOR loops
Message-ID: <1439@csuna.UUCP>
Date: 14 Dec 88 02:31:16 GMT
Reply-To: abcscnuk@csun.UUCP (Naoto Kimura)
Organization: California State University, Northridge
Lines: 50


    I have gotten into some pretty heated discussions regarding the
control variable in a for loop.  I was arguing that it was a bad idea to
use a global variable, in fact it is an error to do so.  I'm arguing
from the ISO standard, while the people I was arguing against were going
by specific implementations that allowed it.

    Should the use of a relatively global variable be allowed as a
control variable for a for loop ?  Should the use of a passed parameter
be allowed as a control variable ?  I say no to both of these.

    One person that I got into an argument with said that the behavior
should be that you can change a control variable, but should not have
any effect on the loop itself.  I don't think that is reasonable.
Consider the confusion over what the variable 'i' should contain when
you use it in several procedures as control variables for a for loop.

    I'd like to know how you feel about the behavior of the following
program.  What should the output be (if the compiler even lets this
code through) ?

program nonsense(input,output);
    var
	i : integer;

    procedure barf;
    begin
	for i := 1 to 10 do
	    write(i:3);
	write('   i=',i)
    end;

    procedure ack;
    begin
	for i := 1 to 10 do begin
	    write('i=',i:2,' ');
	    barf;
	    writeln
	  end
    end;

begin
    for i := 1 to 10 do
	ack
end.

                //-n-\\				Naoto Kimura
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