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From: johnson@cs.uiuc.EDU (Ralph Johnson)
Newsgroups: comp.lang.smalltalk
Subject: Re: PP Smalltalk R4 Query, Bug?
Keywords: help
Message-ID: <1991Mar9.172040.9335@m.cs.uiuc.edu>
Date: 9 Mar 91 17:20:40 GMT
References: <4931@goanna.cs.rmit.oz.au> <1991Mar8.140425.10863@m.cs.uiuc.edu> <3086@laura.UUCP>
Sender: news@m.cs.uiuc.edu (News Database (admin-Mike Schwager))
Reply-To: johnson@cs.uiuc.EDU (Ralph Johnson)
Organization: University of Illinois
Lines: 32

Hubert Baumeister pointed out that my explanation of why the Smalltalk
class library inventers made add: return the argument was completely
wrong, so I'll make a second attempt.

There are two choice, either return the receiver or the argument.
The way things work now, one can either send a message to the the
reciever using cascaded messages or to the argument using parantheses.
The standard example of the first situation is

	aCollection add: thing1;
		    add: thing2;
		    add: thing3

An example of the second situation is

	(aCollection add: OrderedCollection new)
		add: thing1;
		add: thing2

which puts thing1 and thing2 in the OrderedCollection.
If add: returned its argument then the first example could
be recoded without cascaded messages, but the second example
would require a temporary variable.

I am pretty sure that this is the reason for the strange semantics
of add:.  Note that I am not arguing in its favor, I am just
explaining it.  I've had to explain it over and over again,
and I'm pretty tired of it.  In my opinion, a few temporary
variables would be better than a feature that almost everyone
gets wrong at first.  However, it is too late to change it now!

Ralph Johnson -- University of Illinois at Urbana-Champaign