Re: Understanding the Schwartzian transform.

in reply to Understanding the Schwartzian transform.

I was looking at a article ... wanted make sure I was interpreting (pun intended) the mechanism correctly:

:) Consider interpreting the article instead , or one of these (: not sure if this was punny :)

Schwartzian Transform: How do I sort an array by (anything)?
Schwartzian Transform: Schwartzian Transform; Schwartzian Transform
site:perlmonks.org Schwartzian Transform: Guttman-Rosler Transforms; Renaming the Schwartzian Transform; Sorting dates with the Schwartzian Transform
dominus Schwartzian transform: Schwartzian transform; The Perl Hardware Store - Tools You Didn't Know You Needed; Sorting with the Schwartzian Transform (May 06)

Am I close to understanding it? Is the Schwartzian Transform *always* constructed in this manner?

Close, just need some Basic debugging checklist to cement your understanding

$ cd dominus-tmp

$ cat schwartz
#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;

my @sorted_names ;


opendir D, '.' or die $!;
@sorted_names =
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;

opendir D, '.' or die $!;
@sorted_names =
    sort { $b->[1] <=> $a->[1] }
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;

opendir D, '.' or die $!;
@sorted_names =
    map { $_->[0] }
    sort { $b->[1] <=> $a->[1] }
    map { [ $_, -M $_ ] }
    readdir D;
dd \@sorted_names;
__END__


$ perl schwartz
[
  [".", 0.00197916666666667],
  ["..", 0.00247685185185185],
  ["schwartz", 0.000289351851851852],
]
[
  ["..", 0.00247685185185185],
  [".", 0.00197916666666667],
  ["schwartz", 0.000289351851851852],
]
["..", ".", "schwartz"]
[download]

The [ $_, -M $_ ] } part is known as [ $_, expensive_function( $_ ) ]

Comment on Re: Understanding the Schwartzian transform. Select or Download Code

In Section Seekers of Perl Wisdom