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Re: When can I take given as read?

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From:
Larry Wall
Date:
June 17, 2005 11:50
Subject:
Re: When can I take given as read?
Message ID:
20050617185018.GC817@wall.org
On Fri, Jun 17, 2005 at 04:41:53AM +0100, Piers Cawley wrote:
: Suppose I have a simple, single argument recursive function:
: 
:   sub factorial (Int $n) {
:     return 1 if $n == 0;
:     return $n * factorial $n;
:   }
: 
: Can I write that as:
: 
:   sub factorial (Int $n:) {
:     return 1 when 0;
:     return $n * factorial $n;
:   }

As it stands right now, no.  Ordinary subs do not allow invocants.
Arguably, it'd be more consistent if ordinary subs always topicalized
their first argument.  (But blocks have to be handled differently
since they expect to see the outer binding of $_ unless the block itself
rebinds $_.)  On the other hand, it'd probably work if you threw a
"multi" in front of the "sub".

Can anyone think of a good reason not to topicalize the first arg
of ordinary subs these days?  Other than subtle encouragement toward
use of multis?  I suppose it also makes refactoring between subs and
methods more difficult in the case where you're adding an invocant,
though it actually makes it easier in the case where you're just
turning the first sub argument into an invocant because you realize
you've been writing C-style OO code...

6.5 of one, half a baker's dozen of the other...

Larry

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