Re: How to iterate thru entire array with start point other than beginning

Slices are fun:

use strict;
use warnings;

my @month_name = qw(
    January February March April May June July August September
    October November December
    );
    
for my $startMonthIdx (0 .. 11) {
    my @sel = @month_name[$startMonthIdx .. 11, 0 .. $startMonthIdx - 
+1];

    print "$startMonthIdx: @sel\n";
}
[download]

Prints:

0: January February March April May June July August September October
+ November December
1: February March April May June July August September October Novembe
+r December January
2: March April May June July August September October November Decembe
+r January February
3: April May June July August September October November December Janu
+ary February March
4: May June July August September October November December January Fe
+bruary March April
5: June July August September October November December January Februa
+ry March April May
6: July August September October November December January February Ma
+rch April May June
7: August September October November December January February March A
+pril May June July
8: September October November December January February March April Ma
+y June July August
9: October November December January February March April May June Jul
+y August September
10: November December January February March April May June July Augus
+t September October
11: December January February March April May June July August Septemb
+er October November
[download]

Premature optimization is the root of all job security

Comment on Re: How to iterate thru entire array with start point other than beginning Select or Download Code

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Re^2: How to iterate thru entire array with start point other than beginning by soonix (Chancellor) on Sep 02, 2016 at 12:30 UTC
no need to concatenate two ranges. Instead of `my @sel = @month_name[$startMonthIdx .. 11, 0 .. $startMonthIdx - +1];` [download] you can use `my @sel = @month_name[$startMonthIdx - 12 .. $startMonthIdx - 1];` [download] gives the same output as above.	[reply] [d/l] [select]
Re^2: How to iterate thru entire array with start point other than beginning by AnomalousMonk (Archbishop) on Sep 02, 2016 at 17:58 UTC
The only objection I would make to the array slice approaches of GrandFather here or soonix here (++ to both by the way) is that they start to produce strange results for `$startMonthIdx` values outside the `0 .. @month_name` range. This may not be a real problem since one may never endeavor to venture outside this range. The attraction for me of the modulo-`@month_name` approach is that it gives sensible results for any weird positive or negative range whatever. I would prefer to impose any range limits in a separate step and then just reliably handle whatever range emerged from the validation process. c:\@Work\Perl\monks>perl -wMstrict -le "my @months = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec); ;; for my $offset (-25 .. -11) { printf 'offset %3d: ', $offset; my @sel = map $months[ ($_ + $offset) % @months ], -109 .. -95; printf qq{@sel}; print ''; } " offset -25: Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ja +n offset -24: Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Fe +b offset -23: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Ma +r offset -22: Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Ap +r offset -21: Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Ma +y offset -20: Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Ju +n offset -19: May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Ju +l offset -18: Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Au +g offset -17: Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Se +p offset -16: Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oc +t offset -15: Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct No +v offset -14: Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov De +c offset -13: Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ja +n offset -12: Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Fe +b offset -11: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Ma +r [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]