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From: jans@tekecs.UUCP (Jan Steinman)
Newsgroups: net.lang.st80
Subject: Re: The wonderfulness of block arguments
Message-ID: <7593@tekecs.UUCP>
Date: Tue, 2-Sep-86 14:43:54 EDT
Article-I.D.: tekecs.7593
Posted: Tue Sep  2 14:43:54 1986
Date-Received: Wed, 3-Sep-86 04:18:36 EDT
References: <492@randvax.UUCP>
Reply-To: jans@tekecs.UUCP (Jan Steinman)
Organization: Tektronix, Wilsonville OR
Lines: 21
Keywords: arguments

In article <492@randvax.UUCP> obrien@randvax.UUCP (Michael O'Brien) writes:
>If a block argument has the same name as a temporary variable, they seem
>to be the same thing...
>
>It is entirely possible that there is some punning going on, and that if the
>block is not evaluated, the block argument will refer to some other variable
>or to random storage.

Block arguments ARE temporary variables, at least from the Virtual
Machine's point of view.  (The Blue Book has a good discussion of this on
pages 559-560.)  The behavior cited is due to the scoping rules of the
Smalltalk compiler -- temporaries cannot be used before they are declared.
If the "[:blockArgumentName|" construct is thought of as an out-of-place
temporary declaration, the described behavior makes sense.

Block arguments are initialized to "nil", as are all temporary variables.

-- 
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