From: Luke Palmer <[EMAIL PROTECTED]>
Date: October 5, 2005 1:48:54 AM EDT
To: David Storrs <[EMAIL PROTECTED]>
Subject: Re: zip: stop when and where?
Reply-To: Luke Palmer <[EMAIL PROTECTED]>
On 10/4/05, David Storrs <[EMAIL PROTECTED]> wrote:
How about:
@foo = ('a', 'b', 'c');
for @foo ¥ 1..6 :fillin(undef) # a 1 b 2 c 3 undef 4 undef 5
undef 6
for @foo ¥ 1..6 :fillin('') # a 1 b 2 c 3 '' 4 '' 5 '' 6
for @foo ¥ 1..6 :fillin(0) # a 1 b 2 c 3 0 4 0 5 0 6
for @foo ¥ 1..6 :fillin(return) # same as: return ('a', 1, 'b', 2
'c', 3);
A couple of things bother me about this, though:
- Bad endweight on the adverb. It looks like you are modifying the
second list, not the ¥ op
That's because you are.
Good. That makes sense. I did it this way because it seemed like
others on the thread were doing it this way...but it felt wrong at
the time. Glad to see my intuition is not totally useless.
for @foo ¥ 1..6 :fillin(last) # a 1 b 2 c 3
Uh, I don't think that works.
I know it doesn't, I was proposing it as new functionality. The idea
in my head was a bit fuzzy and I probably should have crystallized it
before writing. Had I done so, it might have come out as something
more like this:
@foo = <a b c>;
for @foo ¥ 1..6 :fillin(undef)
# a 1 b 2 c 3 undef 4 undef 5 undef 6
for @foo ¥ 1..6 :fillin('x')
# a 1 b 2 c 3 x 4 x 5 x 6
for @foo ¥ 1..6 :fillin(exception but last)
# a 1 b 2 c 3
FOR_LOOP:for @foo ¥ 1..6 :fillin(exception but last FOR_LOOP)
# zips the lists, never enters the for loop body
for @foo ¥ 1..6 :fillin(exception but return)
# same as: return <a 1 b 2 c 3>; i.e., it returns from a sub
Perhaps 'exception' is spelled 'fail' or 'die' or something like that.
Off the top of my head, I can't think of why you would want to use
the 'exception but return' that I show above--it would return from
the enclosing subroutine, without ever entering the loop body. It
would be a highly obfuscated way to return. However, my
understanding of the current design is that 'return' is just an
exception with a built-in handler, so this is a logical corner case
of what I'm suggesting.
Could something like this syntax be made to work?
for (@foo ¥:fillin(undef) 1..6) but true # a but true, 1 but
true...undef but true, 6 but true
I think you've stumbled upon the reason why we made adverbs come
after
operators.
I'm not quite sure how you are using 'come after operators' here,
since in both of the following the adverb comes after the op (it's
just that in the second, there's something between them):
for (@foo) Y (1..6) :fillin(undef) {...}
for (@foo ¥:fillin(undef) 1..6) {...}
The important thing is the zip, not the fact that you're
filling in with undef.
I would phrase it as "the important thing is what you are doing with
the lists". That encompasses both the operator you are using (zip)
and how that operator will behave (fill in with, in this case, undef).
--Dks
