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Re: Comma Operator

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Larry Wall
January 21, 2004 11:51
Re: Comma Operator
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On Tue, Jan 20, 2004 at 08:12:28PM -0800, Jonathan Lang wrote:
: Joe Gottman wrote:
: >    About a month ago, a thread here suggested that we change the meaning
: > of the comma operator.  Currently, in scalar context the expression
: >     foo(), bar()
: > means "evaluate foo(), discard the result, then return the value of
: > bar()".
: > It was suggested that this be changed to return the 2-element array
: > (foo(), bar()).  Has Larry ruled on this yet?
: Not that I'm aware of.  For the most part, the previous discussion was
: focusing on what to replace the comma with in the case of "discard all but
: the last result", and my impression was that any ruling on the change
: would likely be contingent on the presence or absence of a suitable
: replacement.

I'm a little frustrated because I feel like I've ruled on it several
times, but it never seems to "stick".  I guess that's because it was
never ruled in an Apocalypse, just in email.  But I'm sure I'm on
the record somewhere saying that I think [-1] is sufficient to pick
out the last element of a list.  If nothing else, just a couple of
days ago, but I'm sure I also said it more than once in ancient times.

: That said, 
: >     By the way, even if we do make this change, I think that in void
: > context the expression
: >     foo(), bar()
: > should still simply evaluate its parameters in order for their side-
: > effects.  This would allow comma expressions to remain as-is in loop 
: > statements (formerly for statements), which is where most of them are 
: > found anyway.  
: I do like this suggestion.  In the majority of cases where I've used the
: comma operator, I've either enclosed the whole thing in parentheses to
: turn it into a list, or I've treated it as a sequence of operators where
: even the last result got discarded.  I've rarely been interested in just
: the last result, and I wouldn't mind that functionality being provided by
: means of a C<last> function which evaluates the list parameters for their
: side effects and returns the value of the last list parameter.  

Well, a C<last> function (or method) would be redundant with [-1], though
I'm not totally opposed to redundancy.  ["You can say that again."]


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