Re^4: Using map function to print few elements of list returned by sort function

[jaypal]

With your hint, I was able to do the following

perl -F':' -lane '
push @{$h{$F[1]}}, [$F[0],$_] }{
print $_->[1] for map { splice [sort {$b->[0] <=> $a->[0]} @{$h{$_}}],
+0,4 } keys %h' file
20470:ZM:Samfya:Africa
20149:ZM:Sesheke:Africa
18638:ZM:Siavonga:Africa
699385:ZW:Bulawayo:Africa
61739:ZW:Chinhoyi:Africa
47294:ZW:Chegutu:Africa
37423:ZW:Bindura:Africa

Thanks LanX, your guidance was much appreciated.

[LanX]

this can be simplified (and will work with older perl-versions)

perl -F':' -lane '
push @{$h{$F[1]}}, [$F[0],$_] }{
print $_->[1] for map { ( sort {$b->[0] <=> $a->[0]} @$_ )[0..3] } val
+ues %h' file
20470:ZM:Samfya:Africa
20149:ZM:Sesheke:Africa
18638:ZM:Siavonga:Africa

699385:ZW:Bulawayo:Africa
61739:ZW:Chinhoyi:Africa
47294:ZW:Chegutu:Africa
37423:ZW:Bindura:Africa

Please note that countries with less than 4 cities will have empty lines.

But I'd rather prefer chaining only maps...

update

to avoid empty lines skip the -l option

perl -F':' -ane '
push @{$h{$F[1]}}, [$F[0],$_] }{
print $_->[1] for map { ( sort {$b->[0] <=> $a->[0]} @$_ )[0..3] } val
+ues %h' file
20470:ZM:Samfya:Africa
20149:ZM:Sesheke:Africa
18638:ZM:Siavonga:Africa
699385:ZW:Bulawayo:Africa
61739:ZW:Chinhoyi:Africa
47294:ZW:Chegutu:Africa
37423:ZW:Bindura:Africa

elaboration

values instead of keys

(List)[slice] instead of splice

-l chomps and sets auto-newline in $\

[jaypal]

Thanks Rolf, using values instead of keys does make a lot sense. Thank you for sharing this. :)