Solution to task 2

1 files changed, 75 insertions, 0 deletions

diff --git a/challenge-180/jo-37/perl/ch-2.pl b/challenge-180/jo-37/perl/ch-2.pl
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+++ b/challenge-180/jo-37/perl/ch-2.pl
@@ -0,0 +1,75 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples, $trim); 
+
+run_tests() if $tests || $examples;	# does not return
+$trim //= -1;
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [-trim=LIM] [--] [N1 N2...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+-trim=LIM
+    use LIM as trim limit. Default: -1
+
+N1 N2...
+    List to be trimmed
+
+EOS
+
+sub trim_low :prototype($\@);
+
+
+### Input and Output
+
+trim_low($trim, @ARGV);
+say "@ARGV";
+
+
+### Implementation
+
+# The simplistic statement "grep $_ > $i, @n;" cannot be the solution to
+# a PWC task.  There must be something beyond that.  I presume the given
+# array has to be modified. 
+sub trim_low :prototype($\@) ($low, $arr) {
+    # Moving backwards over the array simplifies things as removing an
+    # element does not change the indices of not yet processed items.
+    for (my $i = $#$arr; $i >= 0; $i--) {
+        splice @$arr, $i, 1 if $arr->[$i] <= $low;
+    }
+    # Returning a ref to the modified array.
+    $arr;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is &trim_low(3, [1, 4, 2, 3, 5]), [4, 5], 'example 1';
+        is &trim_low(4, [9, 0, 6, 2, 3, 8, 5]), [9, 6, 8, 5], 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is do {&trim_low(3, my $arr = [1, 4, 2, 3, 5]); $arr},
+            [4, 5], 'example 1 - modified array';
+        is do {&trim_low(4, my $arr = [9, 0, 6, 2, 3, 8, 5]); $arr},
+            [9, 6, 8, 5], 'example 2 - modified array';
+	}
+
+    done_testing;
+    exit;
+}