I humbly seek wisdom in the form of a better idiom(s). I am regularly find myself needing to review ordered list. I'm not so interested in the nodes but gap from one list item to the next. I have heard this referred to as the fence vs. posts problem. I seek an idiom for

@ = "A", "B", "C";
my @gaps = mesh @l, @l;
pop @gaps; shift @gaps;

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producing the even numbered list "A","B" ,"B","C"?

Then I work with these using the pairs function from List::Util and List::MoreUtils

In code form:


use strict;
use warnings;
use feature 'say';
use List::MoreUtils 'mesh';
use List::Util 'pairs', 'pairfirst', 'pairgrep', 'pairmap';

my @trip =   ("Chicago", "Saint Looey", "Joplin", "OKC", "Amarillo", "
+Gallup", 
            "Flagstaff", "Winona", "Kingman", "Barstow", "San Bernandi
+no", "LA" )  ;


# I seek, not info on the cities, but info on the 
# differences in going from one city to city.
my @legs = mesh  @trip, @trip;
pop @legs; 
shift @legs;
# I seek an idiom for the above three lines.

map { printf  "%15s to %-15s\n", $_->[0],$_->[1]  } pairs @legs;

# Further
# I might have city info as such:
#           $info{Joplin}{state}=>"MO"
# map { if ($info{$_->[0]}{state} ne  $info{$_->[1]}{state}) {say "Man
+n Act!"}  } pairs @legs;


# given the above @cities array how might I produce
#     $info{Joplin}{state}=>"MO"
#
my @states =   ("IL", "MO", "MO", "OK", "TX", "TX", 
                 "AZ", "AZ", "AZ", "CA", "CA", "CA" )  ;

my %info;
# the following does not work!!!
map { $info{$_[0]}{"state"}=$_[1] } pairs mesh @trip, @states;

say "print the hash:";
say  join " ",  %info;

[download]

Thank you

In reply to Fence vs. Posts by rodinski

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