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From: johnson@cs.uiuc.EDU (Ralph Johnson)
Subject: Re: Reference Semantics
Message-ID: <1991Jun10.215822.28034@m.cs.uiuc.edu>
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Date: Mon, 10 Jun 1991 21:58:22 GMT

As a longtime Smalltalk programmer, I don't see how its use
of reference semantics causes problems.

Reference semantics and copy semantics are not just different
styles of programming, they are different *semantics*.  They
mean different things.  Sometimes a programmer wants to have
stateless values, and sometimes a programmer wants to have
objects with state.  A language should support both.

I've tried functional programming in C, and it is hard, mostly
because of the lack of garbage collection.  Programming with
immutable objects and without side effects is not hard in Smalltalk.
I usually partition a system into the "stateless" parts and the
"stateful" parts.  I usually consider it an improvement when I
can convert mutable objects to immutable objects.  That doesn't
happen often, because it is usually pretty obvious which is which.

I can understand how someone who dosen't understand reference
semantics (or copy semantics, for that matter) will have problems
when they first start to use it.  People have trouble with nearly
anything when they first start to use it, including procedures,
side effects, recursion, inheritance: in short, programming!

Improper use of references can certainly cause problems, but
improper use of anything can cause problems.  I shudder when I
see someone passing a "store" in a functional language to 
simulate reference semantics.  Reference semantics makes many
programs simpler.