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Read file, map all lines, sort results and display top 25
this example from a Well House Consultants training course
More on this [link]

This example is described in the following article(s):
   • Mapping an array / list without a loop - how to do it in Perl 6 - [link]
   • Sorting by key or by comparator - Perl 6 - [link]

This example references the following resources:
http://www.wellho.net/data/rstats2015.xyz
http://www.wellho.net/data/rstats2015.txt

Source code: mapper Module: P600
#!/usr/bin/env perl6

# Read file, map all lines, sort results and display top 25

# Data file can be downloaded from http://www.wellho.net/data/rstats2015.xyz
# or from http://www.wellho.net/data/rstats2015.txt ... be careful not to
# convert tabs to spaces as the program relies on a tab seperated file!

sub getGrowth($text) {
        my @fol = $text.split("\t");
        my $pg = 1.0;
        $pg = @fol[*-1] / @fol[7] unless "NULL" ~~ @fol[*-1] | @fol[7];
        (@fol[1],@fol[2],@fol[7],@fol[*-1],$pg)
        }

my @stations = slurp("rstats2015.txt").chomp.split("\n");
my @opposite = @stations>>.&getGrowth;

@opposite = @opposite.sort({@$^a[4]});

for @opposite[0..25] -> @record {
        say @record.join(", ")
}

=finish

WomanWithCat:perl6 grahamellis$ perl6 mapper
ELO, NG19 9LH, 1310, 88 , 0.067176
LLA, LL42 1AZ, 16198, 1964 , 0.121250
ACK, NE65 4DE, 917, 206 , 0.224646
HEL, DN14 0QN, 714, 182 , 0.254902
CUA, IV27 4ET, 2016, 530 , 0.262897
COE, PL14 7LL, 96, 26 , 0.270833
PIL, BS35 4JT, 245, 68 , 0.277551
GTN, CF11 8UY, 601025, 182814 , 0.3041704
PEG, NE61 6SJ, 3564, 1114 , 0.312570
ABH, LL53 6PJ, 1038, 326 , 0.314066
LEL, TR26 3DS, 8697, 2874 , 0.330459
DNY, YO21 2JL, 23729, 8440 , 0.355683
ISP, OX5 3ED, 18988, 6858 , 0.361175
CLI, M27 8LL, 417, 152 , 0.364508
WBD, DN14 0HH, 1852, 676 , 0.365011
IBM, PA16 0XB, 128741, 47376 , 0.3679947
SWO, CT15 4JH, 18282, 6822 , 0.373154
TPC, PE24 4NL, 738, 284 , 0.384824
GFF, CF81 8LT, 8997, 3606 , 0.400800
CPN, EX37 9DZ, 472, 192 , 0.406780
ADM, CT3 3JE, 53898, 22374 , 0.415117
TEA, DL2 1NL, 74, 32 , 0.432432
WOS, WR4 9EJ, 1355790, 595402 , 0.4391550
BMF, HU15 1RQ, 2912, 1304 , 0.447802
BAV, DN19 7ET, 3521, 1638 , 0.465209
ECS, NR16 2JG, 2358, 1098 , 0.465649
WomanWithCat:perl6 grahamellis$

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