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0 pointsdded12y ago0 comments

The Python .sort() method sorts in-place. The sorted() function returns a sorted copy, leaving the original untouched.

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I realize this is drifting off topic, and I could well believe the current Rakudo implementation doesn't actually save the memory (I could believe it does, I just don't know) but P6, for any method, including sort:

    my $a = [2,1]; say $a.sort;  say $a # 1 2 2 1
    my $a = [2,1]; say $a.=sort; say $a # 1 2 1 2

This riffs off the general op= syntax:

    my $a = 1; say $a +  1; say $a # 2 1
    my $a = 1; say $a += 1; say $a # 2 2

orblivion12y ago

I meant I didn't understand the difference between Python's sort(key=..) and what's described here for Perl.

_ZeD_12y ago

what is described for perl is python's sort(cmp=...)

orblivion12y ago

Hmm? I thought the whole point of the article was "Most people know about sort(cmp=), which takes two parameters. But check out sort(key=), it only takes one parameter, which means the key function only has to run once per item", but for Perl.

raiph12y ago

That's my understanding too.

Lisp had a nice idiom that Randal Schwartz translated in to Perl 5 in 1994 which became known as the Schwartzian Transform: http://en.wikipedia.org/wiki/Schwartzian_Transform

It seems from the comments here that Python's key and cmp args are Python's equivalent to the ST. I'm surprised by the comment that Python 3 removed cmp. Perhaps that's a temporary omission.

This HN is about an advent article for Perl 6, which covers the same territory. Based on a look at the Rakudo code, it only implements a single custom sort closure (equivalent to Python's cmp) OR a single key closure (equivalent to Python's key).

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raiph12y ago

    my $a = [2,1]; say $a.sort;  say $a # 1 2 2 1
    my $a = [2,1]; say $a.=sort; say $a # 1 2 1 2

This riffs off the general op= syntax:

    my $a = 1; say $a +  1; say $a # 2 1
    my $a = 1; say $a += 1; say $a # 2 2

orblivion12y ago

I meant I didn't understand the difference between Python's sort(key=..) and what's described here for Perl.

_ZeD_12y ago

what is described for perl is python's sort(cmp=...)

orblivion12y ago

raiph12y ago

That's my understanding too.

Lisp had a nice idiom that Randal Schwartz translated in to Perl 5 in 1994 which became known as the Schwartzian Transform: http://en.wikipedia.org/wiki/Schwartzian_Transform

It seems from the comments here that Python's key and cmp args are Python's equivalent to the ST. I'm surprised by the comment that Python 3 removed cmp. Perhaps that's a temporary omission.

1 more reply

j / k navigate · click thread line to collapse