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Postings from December 2004
In article <20041205093023.GA26381@navi.cx>,
luke@luqui.org (Luke Palmer) wrote:
>But what we'd really like to do is: given the user knows what push/pop
>do, what would they *guess* to mean shift (I tend to think that this
>is a very good technique for naming).
>And, well, I'm thinking pull. So it's a toss-up between shift/unshift
>and put/pull.
I think "push" and "pull" fairly naturally could be taken to refer to the
front of an array; you might even argue that the natural direction for
something to "pop" is away from you (i.e. off the back)
The problem I have with push/pull referring to opposite ends is that the
same person is doing the pushing and the pulling, so both words ought to
apply to the same end of the array (the front end), which violates the
comp-sci-y expectations. (And although normally I'm happy to chuck CS
jargon out the window, because so much of it is really bad, the push/pop
thing goes pretty deep.) Not to mention everyone coming from Perl <6.
Though if we had "push" without "pop", that wouldn't be as bad.
I guess we could always use prepend/append, pull/pop. You might not guess
what they meant, but once you know, I think the meanings are reasonably
"obvious". (Dislike typing though I may, I'm hesitant to suggest "prep"
and "app".)
Hm, actually counting letters, "prepend" is no longer than "unshift" (and
if not a real word, is at least used as one more often than "unshift" is).
In fact, prepend/append/pull/pop altogether are only one letter more than
push/pop/shift/unshift. So those are now officially my preferred
replacements.
But if we want something that makes it immediately obvious what end of the
array we're messing with.. something visually obvious... ooh, this sounds
like a job for Unicode!! (Just kidding. Sort of.) We've already got
those lovely pipe operators to build on, and they can already do
assignment; if you can go from = to +=, why not from <== to +<==?
@a <== $foo, $bar; # @a=($foo, $bar)
$foo, $bar ==> @a; # ditto
@a +<== $foo, $bar; # push @a, $foo, $bar
$foo, $bar ==>+ @a; # unshift @a, $foo, $bar
@a -==> $foo, $bar; # ($bar, $foo) = (pop @a, pop @a)
$foo, $bar <==- @a; # ($foo, $bar) = (shift @a, shift @a)
The + or - tells you whether you're adding on or taking away, and the
arrow points to (or from) the end of the array you're doing it to. (I
know some people will hate four symbols in a row. That's why we have
seven-letter alternatives like "prepend".)
I was going to say an advantage over old-fashioned pop/shift is that you
could remove more than one element at a time, but there isn't any reason
for their P6 versions not to return as many items as are want()ed, is
there?
The bad news (assuming anyone actually thinks there's anything good in the
above suggestion) is that since +<== and friends are assignment operators,
you can't just do foobar( @a-==>, $x, $y). Um, unless -==> could be made
to work as a unary operator. Which even I don't think I like. =) So we
should keep the wordy versions too.
-David "pull goes the weasel" Green
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