Re: seeking golfing advice
On Thu, May 17, 2012 at 3:14 AM, Aristotle Pagaltzis pagalt...@gmx.de wrote:
* Mike Erickson m...@quidquam.com [2012-05-16 15:45]:
If you don't care about order, but just want those elements, you can
also do:
keys%{{@a}}
There is more than order that gets lost. If you use `keys` you also get
everything back stringified – undefs are lost and references break. If
you use `values` these problems go away… except that to get the odd-
index elements from it you have to `reverse` the array, at which point
a not-especially-golfed grep is shorter.
So you'd want
values%{{1,@a}}
then
Re: seeking golfing advice
* Steve Fink sph...@gmail.com [2012-05-18 10:25]:
On Thu, May 17, 2012 at 3:14 AM, Aristotle Pagaltzis pagalt...@gmx.de wrote:
* Mike Erickson m...@quidquam.com [2012-05-16 15:45]:
If you don't care about order, but just want those elements, you
can also do:
keys%{{@a}}
There is more than order that gets lost. If you use `keys` you also
get everything back stringified – undefs are lost and references
break. If you use `values` these problems go away… except that to
get the odd-index elements from it you have to `reverse` the array,
at which point a not-especially-golfed grep is shorter.
So you'd want
values%{{1,@a}}
then
D’oh!
Re: seeking golfing advice
From: Aristotle Pagaltzis pagalt...@gmx.de
Subject: Re: seeking golfing advice
To: fwp@perl.org
Date: Friday, May 18, 2012, 5:29 AM
* Steve Fink sph...@gmail.com
[2012-05-18 10:25]:
On Thu, May 17, 2012 at 3:14 AM, Aristotle Pagaltzis
pagalt...@gmx.de
wrote:
* Mike Erickson m...@quidquam.com
[2012-05-16 15:45]:
If you don't care about order, but just want
those elements, you
can also do:
keys%{{@a}}
There is more than order that gets lost. If you
use `keys` you also
get everything back stringified – undefs are
lost and references
break. If you use `values` these problems go
away… except that to
get the odd-index elements from it you have to
`reverse` the array,
at which point a not-especially-golfed grep is
shorter.
So you'd want
values%{{1,@a}}
then
D’oh!
D::oh is right. You get an unwanted extra undef at the end of such list.
Re: seeking golfing advice
* Mike Erickson m...@quidquam.com [2012-05-16 15:45]:
If you don't care about order, but just want those elements, you can
also do:
keys%{{@a}}
There is more than order that gets lost. If you use `keys` you also get
everything back stringified – undefs are lost and references break. If
you use `values` these problems go away… except that to get the odd-
index elements from it you have to `reverse` the array, at which point
a not-especially-golfed grep is shorter.
--
*AUTOLOAD=*_;sub _{s/$/$/;s/(.*):://;wantarray//substr$_,-1,1,,$/;print;$1}
Just-another-Perl-hack;
#Aristotle Pagaltzis // http://plasmasturm.org/
Re: seeking golfing advice
* Pau Amma paua...@gundo.com [2012-05-16 14:55]:
If, as it sounds, you want to balance golfiness and strictness, you
could also say:
@array[grep $_%2, keys @array]
(or @array[grep $_%2^1, keys @array] if you set $[ to 1 - but you
didn't do that, right? :-) )
Btw, `keys@foo` and `0..$#foo` are equally long… but the latter works
with old perls (advantage production) *and* looks more line-noisy
(advantage golf).
And if you have an array to work with in the first place, you can also
@array[map 1+$_*2, 0..$#array/2]
which is 3 characters longer than the grep version in exchange for doing
half as much work. (For even elements, the map and grep solutions would
yield exactly equally long code, with half-as-much-work still applying.)
--
*AUTOLOAD=*_;sub _{s/$/$/;s/(.*):://;wantarray//substr$_,-1,1,,$/;print;$1}
Just-another-Perl-hack;
#Aristotle Pagaltzis // http://plasmasturm.org/
Re: seeking golfing advice
btw here is an example :
the code, applied on (1, 2, 3, 4) would return (1, 3). Thanks
On 16 May 2012 13:15, damien krotkine dkrotk...@gmail.com wrote:
Hi,
I'm using this code to get a list of only the odd elements of an
array. The resulting list must have the same order as the array.
map { state $f; ($_) x (++$f%2) } @array;
I'm looking for advice to make it shorter or nicer. Everything in perl
5.12 is allowed, but must pass use strict. I've failed at using the
'..' operator to act as a flip/flop operator...
thanks,
dams
Re: seeking golfing advice
On 16.05.2012 13:19, damien krotkine wrote:
btw here is an example :
the code, applied on (1, 2, 3, 4) would return (1, 3). Thanks
On 16 May 2012 13:15, damien krotkinedkrotk...@gmail.com wrote:
Hi,
I'm using this code to get a list of only the odd elements of an
array. The resulting list must have the same order as the array.
map { state $f; ($_) x (++$f%2) } @array;
I'm looking for advice to make it shorter or nicer. Everything in perl
5.12 is allowed, but must pass use strict. I've failed at using the
'..' operator to act as a flip/flop operator...
thanks,
dams
Isn't this what grep is for?
1 #!perl
2 use strict;
3 my @array=(1,2,3,4);
4 my $f;
5 my @result = grep {++$f%2} @array;
6 print @result\n;
--
*Daniel Cutter*
s/\b[^a]/\u$/g,s;$;,;,print for join$,,map{('acehjklnoprstu'
=~m(.)g,$)[/\d/?$_:hex]}q(4dbce078c32ae92a6e30152aff)=~m(.)g
Re: seeking golfing advice
damien krotkine dkrotk...@gmail.com writes:
I'm using this code to get a list of only the odd elements of an
array. The resulting list must have the same order as the array.
map { state $f; ($_) x (++$f%2) } @array;
If you want only to get some elements of a list is is much more obvious
to use grep instead of map:
grep { ++$f%2 } @array
Then use the magical flip-flop variable:
grep { $|-- } @array
And remove unneeded syntax
grep$|--,@array
//Makholm
Re: seeking golfing advice
It's not clear whether you want every other element, beginning with the first
or every numeric element with the property 'odd'. Your example doesn't clear
that up at all. :-)
If it's the latter you want:
map { $_ 1 ? $_ : () } @l;
--- On Wed, 5/16/12, damien krotkine dkrotk...@gmail.com wrote:
From: damien krotkine dkrotk...@gmail.com
Subject: Re: seeking golfing advice
To: fwp@perl.org
Date: Wednesday, May 16, 2012, 7:19 AM
btw here is an example :
the code, applied on (1, 2, 3, 4) would return (1, 3).
Thanks
On 16 May 2012 13:15, damien krotkine dkrotk...@gmail.com
wrote:
Hi,
I'm using this code to get a list of only the odd
elements of an
array. The resulting list must have the same order as
the array.
map { state $f; ($_) x (++$f%2) } @array;
I'm looking for advice to make it shorter or nicer.
Everything in perl
5.12 is allowed, but must pass use strict. I've failed
at using the
'..' operator to act as a flip/flop operator...
thanks,
dams
Re: seeking golfing advice
Peter Makholm pe...@makholm.net writes:
damien krotkine dkrotk...@gmail.com writes:
I'm using this code to get a list of only the odd elements of an
array. The resulting list must have the same order as the array.
map { state $f; ($_) x (++$f%2) } @array;
Wow, you asked for golfing advice in the subject and a nice solution in
the actual text. Those requirements are quite often very incompatible.
If you want only to get some elements of a list is is much more obvious
to use grep instead of map:
grep { ++$f%2 } @array
This is probably as nice as it gets. For strictness I would just declare
$f as a lexical variable just outside the grep. But asking for golfing
advice is not compliant with strictness or niceness.
And remove unneeded syntax
grep$|--,@array
I think this would be the golfing solution, but as with everything alse
related to perl golfing don't use it in production code.
//Makholm
Re: seeking golfing advice
And of course, use grep, as others have said.
@list[ grep !$_%2, 0..$#list ];
that gets you every other element, beginning with the first.
--- On Wed, 5/16/12, John Douglas Porter johndpor...@yahoo.com wrote:
From: John Douglas Porter johndpor...@yahoo.com
Subject: Re: seeking golfing advice
To: fwp@perl.org
Date: Wednesday, May 16, 2012, 7:35 AM
It's not clear whether you want
every other element, beginning with the first or every
numeric element with the property 'odd'. Your example
doesn't clear that up at all. :-)
If it's the latter you want:
map { $_ 1 ? $_ : () } @l;
--- On Wed, 5/16/12, damien krotkine dkrotk...@gmail.com
wrote:
From: damien krotkine dkrotk...@gmail.com
Subject: Re: seeking golfing advice
To: fwp@perl.org
Date: Wednesday, May 16, 2012, 7:19 AM
btw here is an example :
the code, applied on (1, 2, 3, 4) would return (1, 3).
Thanks
On 16 May 2012 13:15, damien krotkine dkrotk...@gmail.com
wrote:
Hi,
I'm using this code to get a list of only the odd
elements of an
array. The resulting list must have the same order
as
the array.
map { state $f; ($_) x (++$f%2) } @array;
I'm looking for advice to make it shorter or
nicer.
Everything in perl
5.12 is allowed, but must pass use strict. I've
failed
at using the
'..' operator to act as a flip/flop operator...
thanks,
dams
Re: seeking golfing advice
Hi all,
thanks for the quick answers :)
first of all, despite my attempt to clear things up with an example, I
failed :) What I wante is every other element, beginning with the
first, so :
( 'foo', 3, 42, 'bar) should become ( 'foo', 42).
Indeed grep is much better. As the code is used in a more complex
structured I got lost and confused and ended up using map, blah.
$|-- was what I was looking for :)
About golfing and strictness I am well aware that the two are
incompatible. What I originally meant is to get something with a sane
balance between the two.
Finally, one question : why is $|-- not recommended in production, if
the following conditions are met : I'm not running in threads, not in
an event-loop that might be affected by $| being set, and I'll take
care of resetting $| appropriately at the end.
Even in this case, wouldn't you recommend using $| ?
Thanks again
On 16 May 2012 13:36, Peter Makholm pe...@makholm.net wrote:
Peter Makholm pe...@makholm.net writes:
damien krotkine dkrotk...@gmail.com writes:
I'm using this code to get a list of only the odd elements of an
array. The resulting list must have the same order as the array.
map { state $f; ($_) x (++$f%2) } @array;
Wow, you asked for golfing advice in the subject and a nice solution in
the actual text. Those requirements are quite often very incompatible.
If you want only to get some elements of a list is is much more obvious
to use grep instead of map:
grep { ++$f%2 } @array
This is probably as nice as it gets. For strictness I would just declare
$f as a lexical variable just outside the grep. But asking for golfing
advice is not compliant with strictness or niceness.
And remove unneeded syntax
grep$|--,@array
I think this would be the golfing solution, but as with everything alse
related to perl golfing don't use it in production code.
//Makholm
Re: seeking golfing advice
damien krotkine dkrotk...@gmail.com writes: Indeed grep is much better. As the code is used in a more complex structured I got lost and confused and ended up using map, blah. $|-- was what I was looking for :) No, reading my posts again it I see that it clearly doesn't do what you ask for. You are actually looking for --$|. Finally, one question : why is $|-- not recommended in production, if the following conditions are met : I'm not running in threads, not in an event-loop that might be affected by $| being set, and I'll take care of resetting $| appropriately at the end. It depends on an obscure, undocumented feature of a magic variable, which unless used correct may have an unintended action at a distance. This makes the code hard to maintain for the next developer (which might be youself 14 days down the road). What do you think you are optimizing for? I would guess that the $| is also a bit slower, as it needs to at least test if the filehandle needs to be flushed even though you know that no one had the chance to write to it. So basically you are trading 8 characters for readability and probably speed. Why do you want that? //Makholm
Re: seeking golfing advice
On 16 May 2012 14:02, Peter Makholm pe...@makholm.net wrote: damien krotkine dkrotk...@gmail.com writes: Indeed grep is much better. As the code is used in a more complex structured I got lost and confused and ended up using map, blah. $|-- was what I was looking for :) No, reading my posts again it I see that it clearly doesn't do what you ask for. You are actually looking for --$|. Oops yes, --$| indeed, sorry. [ ... ] So basically you are trading 8 characters for readability and probably speed. Why do you want that? For fun, purely. I'll stick with $f % 2 for now, it seems a right balance compared to the code lying around. dams
Re: seeking golfing advice
On Wed, May 16, 2012 12:25 pm, damien krotkine wrote: On 16 May 2012 14:02, Peter Makholm pe...@makholm.net wrote: [ ... ] So basically you are trading 8 characters for readability and probably speed. Why do you want that? For fun, purely. I'll stick with $f % 2 for now, it seems a right balance compared to the code lying around. If, as it sounds, you want to balance golfiness and strictness, you could also say: @array[grep $_%2, keys @array] (or @array[grep $_%2^1, keys @array] if you set $[ to 1 - but you didn't do that, right? :-) )
Re: seeking golfing advice
On 05/16/2012 07:46 AM, damien krotkine wrote:
Hi all,
thanks for the quick answers :)
first of all, despite my attempt to clear things up with an example, I
failed :) What I wante is every other element, beginning with the
first, so :
( 'foo', 3, 42, 'bar) should become ( 'foo', 42).
If you don't care about order, but just want those elements, you can
also do:
keys%{{@a}}
{@a}being a hash ref constructed from @a
%{ }dereferencing that hash ref
keyspulling out the keys, ie. the odd elements of the orig. list
hth,
Mike
Re: seeking golfing advice
On Wed, May 16, 2012 at 04:40:40AM -0700, John Douglas Porter wrote: And of course, use grep, as others have said. @list[ grep !$_%2, 0..$#list ]; that gets you every other element, beginning with the first. ! has higher precedence than %, so this actually gets you just the first element. You need to add parentheses to get the correct result: @list[grep!($_%2),0..$#list]; There are a couple ways to shave a character from that: @list[grep$_%2-1,0..$#list]; @list[grep$_+11,0..$#list]; Ronald
