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Ken, thanks for your writeup, including forcing me to learn a bit about Test -- I needed that! :-)

I'd rather stick with Perl's slice capability since it reads more cleanly (to me, anyway) and doesn't require copying and modifying the source array. Here's how I ended up implementing and testing pyrange():

#!/usr/bin/env perl use v5.36; use constant { AREF => 0, PYTHON => 1, EXP => 2, }; use Test::More; my @test_array = 'a' .. 'g'; my @tests = ( [\@test_array, '[:3]', 'abc'], [\@test_array, '[:-3]', 'abcd'], [\@test_array, '[3:]', 'defg'], [\@test_array, '[-3:]', 'efg'], [\@test_array, '[-3:-1]', 'ef'], # testing double-ended ranges [\@test_array, '[-3:-3]', ''], [\@test_array, '[3:-1]', 'def'], ); plan tests => 0+@tests; for my $test (@tests) { is get_array_slice_by_python_expr($test->@[AREF, PYTHON]), $test->[EXP], "Testing: $test->[PYTHON]"; } sub get_array_slice_by_python_expr ($aref, $python) { ### $re modified to return undef instead of '' when endpoint omitt +ed state $re = qr{^ \[ ( -? \d+ )? : ( -? \d+ )? \] $}x; my ($start, $stop) = $python =~ $re; my $range_aref = pyrange($aref, $start, $stop); return join '', @$range_aref; } sub pyrange($aref, $start=undef, $stop=undef) { if (!defined $start) { $start = 0; } elsif ($start < 0) { $start = @$aref + $start; } if (!defined $stop) { $stop = $#$aref; } elsif ($stop >= 0) { $stop = $stop - 1; } else { $stop = @$aref + $stop - 1; } return [@$aref[$start .. $stop]]; }
Output:
$ ./test 1..7 ok 1 - Testing: [:3] ok 2 - Testing: [:-3] ok 3 - Testing: [3:] ok 4 - Testing: [-3:] ok 5 - Testing: [-3:-1] ok 6 - Testing: [-3:-3] ok 7 - Testing: [3:-1]

In reply to Re^2: Converting python list range expressions to perl by ibm1620
in thread Converting python list range expressions to perl by ibm1620

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