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From: fmarh@minyos.xx.rmit.oz.au (Robert Hinterding)
Newsgroups: comp.lang.smalltalk
Subject: Re: Nested Control Structures Within Iterators
Message-ID: <1991Apr8.234951.22900@minyos.xx.rmit.oz.au>
Date: 8 Apr 91 23:49:51 GMT
References: <41040@cup.portal.com>
Organization: Victoria University of Technology, Melbourne Australia.
Lines: 42

In article <41040@cup.portal.com> Will@cup.portal.com (Will E Estes) writes:
>Can someone explain to me whether it is possible to place another 
>control structure on the same line as an iterator?  Say, for instance,
>that I'm iterating across a file stream and I want to continue to
>do so only while some condition is true.
>
>	input do:
>	[
>		:char |
>		output nextPut: char.
>		"more code here"
>	].
>
>Now what I would like to do is qualify the iteration of do: such that
>when some condition becomes true we stop iterating?  One thought that
>comes to mind is an equivalent to the C control structure BREAK, but
>I was not able to find this.  Is there someone of achieving the effect
>of BREAK?  And if not is there some way of further qualifying the
>iterator statement?
>
>Thanks,
>Will Estes        Internet: Will@cup.portal.com                  
>                  UUCP: apple!cup.portal.com!Will

The problem is that do: is for iterating over the whole collection.  To
do what you want, you need to use a different method.  As you stated 
that input was a file stream a way of doing it is shown below.

	[ condition and:[ input atEnd not] ]
	whileTrue:[ 
		input next "more code here"
        ]

whileTrue is a method for class Context, atEnt and next are methods
for class FileStream in the example.  
I hope this helps you.

-- 
Robert Hinterding                             fmarh@minyos.xx.rmit.oz.au
Victoria University of Technology             Phone +61 3 6884686
PO Box 64, Footscray 3011                     Fax: +61 3 687 7632
Australia