From: Paul Prescod <paulp@...>
Date: 2001-06-22T06:39:25+09:00
Subject: [ruby-talk:16727] Re: Simulating call-by-reference in Ruby

Tobin Baker wrote:
> 
>...
> 
> Python doesn't have anything like Perl's reference operator, so the
> mapping spec recommends passing inout parameters like in parameters,
> and returning them in a tuple together with the return value (if any)
> and all out parameters.  To me this is somewhat inelegant and does a
> rather poor job of emulating inout semantics, but there may be no
> alternative in Python.  In Ruby, however, we *can* simulate reference
> parameters by having the caller pass a symbol instead of the variable
> itself, getting the value of the variable for that symbol from the
> caller's context (using eval), and then using eval again to write
> another value into that variable.  

I think that your proposed solution is actually possible in Python but I
question your basic premise. Doing things in a way that closely emulates
"inout semantics" is less important than doing things in a way that is
idiomatic in the actual language. If languages like Python and Ruby
don't have call-by-reference, I think it is more confusing than helpful
to add it to the language through tricks. Python functions that want to
return multiple arguments return tuples. Java uses holder classes[1].
Ruby has tuples also, what's wrong with using them?

http://industry.ebi.ac.uk/~senger/ws-corba/home/talks/corba_java_mapping/tsld006.htm
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