Path: utzoo!mnetor!uunet!tektronix!tekcrl!jans
From: jans@tekcrl.TEK.COM (Jan Steinman)
Newsgroups: comp.lang.smalltalk
Subject: Re: Question concerning behavior of assignment and copy methods
Message-ID: <2480@tekcrl.TEK.COM>
Date: 31 Mar 88 20:36:45 GMT
Organization: Tektronix Inc., Beaverton, Or.
Lines: 33

<I am writing an intelligent chess board in STV to help in some analysis; I set 
the initial position of the board with a literal array. I was surprized the 
second time I ran the program and, after initialization, got the old board.>

Literal arrays are not constants in Smalltalk, and assignment is by reference.  
Therefore:

	b _ a _ 'Crazy Jane'.
	a at: 8 put: $u.
	Transcript show: b.

will print 'Crazy June'.  If this is done in a workspace, the visible text does 
not change -- the literal that changes is int the DoIt compiled method.  If 
this code is placed in a method, a and b will indeed get initialized to 'Crazy 
June' the second time the method is executed.

Note that the source code of such a method, like the visible text in the 
workspace example, does not change, which can cause considerable confusion!

<I've used lost of pointers and indirection in C; if someone would help me and 
tell me what's going on, I will understand!>

The preceeding Smalltalk code is roughly the similar to the following C code:

	static char a[] = "Crazy Jane";
	char *b;
	b = a;
	a[7] = 'u';
	printf("%s", b);

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