Re^3: Sorting a "tuple" by the second value

[johngg]

You could combine the steps in your get_links() and sort_and_store() subroutines into one process.

knoppix@Microknoppix:~$ cat spw964070.in
abc peter
def jack
ghi zak
jkl ben
mno mick
pqr alan
knoppix@Microknoppix:~$ perl -Mstrict -wE '
> open my $inFH, q{<}, q{spw964070.in}
>    or die qq{open: < spw964070.in: $!\n};
> open my $outFH, q{>}, q{spw964070.out}
>    or die qq{open: > spw964070.out: $!\n};
> 
> print $outFH
>    map  { $_->[ 0 ] }
>    sort { $a->[ 2 ] cmp $b->[ 2 ] }
>    map  { [ $_, split ] }
>    <$inFH>;
> 
> close $inFH 
>    or die qq{close: < spw964070.in: $!\n};
> close $outFH
>    or die qq{close: > spw964070.out: $!\n};'
knoppix@Microknoppix:~$ cat spw964070.out 
pqr alan
jkl ben
def jack
mno mick
abc peter
ghi zak
knoppix@Microknoppix:~$

Sticking to your subroutines, it would be more efficient for get_links() to return a reference to @info than the huge array itself, like so:-

    ...
    return \ @links;
}

sub sort_and_store {
    my $refToLinks = get_links();
    my @sorted_links = sort { $a->[1] cmp $b->[1] } @$refToLinks;
    ...

I hope these points are helpful.

[thmsdrew]

Definitely helpful. I need to learn more about referencing and when it's best to use. Thanks!

[sundialsvc4]

“Referencing” is a drop-dead simple idea, actually:   a reference is “a tiny thing” that refers to something else in memory.   That thing which is referred-to may be big or small, and there may be just one reference to it or a great many.   But each reference is very small and cheap.   So, for example, if you have in-memory a list of “big records,” you can swap and manipulate and what-have-you those records just by playing around with lists (or arrays, or hashes) of references to them:   nothing actually “moves.”   This lets you build up arbitrarily-complex data structures very easily, and to work with them very efficiently.   (Want to sort the same list of records by three separate keys at once, all in-memory, keeping all three lists, without making duplicate copies of anything?   Feel Free.™)   It’s one of the hallmarks of Perl and one of the compelling reasons for using this language.