Path: sran265!katsu
From: katsu@sra.co.jp (WATANABE Katsuhiro)
Message-ID: <KATSU.94Feb22183154@sran14.sra.co.jp>
Date: 22 Feb 1994 09:31:53 GMT
Organization: Software Research Associates, Inc.,Japan
In-reply-to: iwm@doc.ic.ac.uk's message of 11 Feb 1994 20:23:39 GMT
Newsgroups: comp.lang.smalltalk
Subject: Re: leaving a block ?
Distribution: world
References: <IWM.94Feb11202339@swan.doc.ic.ac.uk>

In article <IWM.94Feb11202339@swan.doc.ic.ac.uk> iwm@doc.ic.ac.uk (Ian Moor) writes:

> Is it possible to leave a block without leaving the surrounding method ?
> for example in using do:
> 
> s do: [ :element | (element isMemberOf: Thing) ifTrue: [ found := true. ..? ]]
> " More code to be done"

As have been shown already, using detect: or adding special method
into BlockClosure will solve the problem. But, let me propose yet
another way, which can be applicable on PPS Smalltalk only:

| signal result |
signal := Object informationSignal newSignal.
result := signal
		handle: [:ex | ex returnWith: ex parameter]
		do: [
			s do: [:element |
				(element isMemberOf: Thing)
				ifTrue: [signal raiseWith: element]].
			nil].
"check if the result is nil or not"

I'd say it's rather flexible because you can exit a block (to say,
raise the signal) even from deep inner method which you called from
the block.

--
WATANABE Katsuhiro <katsu@sra.co.jp>
Software Research Associates, Inc. (Tokyo JAPAN)