RE: RE: Re: Sorting on Section Numbers

There is a slight bug in this solution, it drops letters.
Using the above test data, the following list is generated:
1, 1.2, 2, 2.1.7, 2.2, 2.13, 3.4, 10.1, 10.1, 10.10
which dropped the letters from the section headings.
Here's my version:

@sorted = 
    map {$_->[0], ", "}
    sort {$a->[0] <=> $b->[0]}
    map {[$_, pack ("N*", $_)]}
    
@unsorted;
[download]

it works the same way, but I substituted in a Schwartzian transform to cache the original value of the heading instead of unpacking it again later. According to some tests with Benchmark, it's about 40% faster than doing the unpack later.
Plus it keeps letters intact.

Comment on RE: RE: Re: Sorting on Section Numbers Download Code

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RE: RE: RE: Re: Sorting on Section Numbers by DrManhattan (Chaplain) on Jul 28, 2000 at 18:37 UTC
`@sorted = map {$_->[0], ", "} sort {$a->[0] <=> $b->[0]} map {[$_, pack ("N*", $_)]} @unsorted;` [download] For anyone who doesn't understand what the above code does, here are some nodes with explanations of the technique and some interesting discussion: <list> Schwartzian Transform Sorting IP Addresses Quickly A Fresh Look at Efficient Perl Sorting (thanks davorg) -Matt	[reply] [d/l]
RE: RE: RE: Re: Sorting on Section Numbers by chip (Curate) on Jul 28, 2000 at 22:40 UTC
Of course that solution drops letters. That was the whole point, demonstrating that things get a lot simpler without them. Quoting myself: If we simplify the problem space by eliminating the alphanumerics, things get even neater. -- Chip Salzenberg, Free-Floating Agent of Chaos	[reply]
RE {4} Sorting on Section Numbers by turnstep (Parson) on Jul 28, 2000 at 21:27 UTC
> it works the same way, but I substituted in a Schwartzian transform to cache the original > value of the heading instead of unpacking it again later. According to some tests with > Benchmark, it's about 40% faster than doing the unpack later. Plus it keeps letters intact. Unfortunately, there are two problems with this code: `@sorted = map {$_->[0], ", "} sort { $a->[0] <=> $b->[0]} map {[$_, pack ("N", $_)]} @unsorted;` [download] First, the map arguments should be reversed or the sort subscripts should be "1" not "0". As it is, all the code does is a simple sort, and ignores the whole pack part! Second, even when it is fixed, it does not quite sort correctly: `@unsorted = qw(2 1.2a 2.2 1.2 1.1a); ## A fixed version: @sorted = map {$_->[0], ", "} sort { $a->[1] <=> $b->[1]} map {[$_, pack ("N", $_)]} @unsorted; print @sorted, "\n"; ## produces: 1.2a, 1.1a, 1.2, 2, 2.2` [download]	[reply] [d/l] [select]