Solution to task 1

1 files changed, 64 insertions, 0 deletions

diff --git a/challenge-119/jo-37/perl/ch-1.pl b/challenge-119/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..b551210f44
--- /dev/null
+++ b/challenge-119/jo-37/perl/ch-1.pl
@@ -0,0 +1,64 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [N ...] 
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N ...
+    swap nibbles in N
+
+EOS
+
+
+### Input and Output
+
+say swap_nibbles($_) for @ARGV;
+
+
+### Implementation
+
+# This works portably for N < 2**32 and potentially up to N < 2**64.  No
+# need to restrict to N < 256.
+sub swap_nibbles {
+    no warnings 'portable';
+	hex unpack 'h*', pack 'J>', shift;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is swap_nibbles(101), 86, 'example 1';
+        is swap_nibbles(18), 33, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is swap_nibbles(0), 0, 'all zero';
+        is swap_nibbles(255), 255, 'all one';
+        is swap_nibbles(129), 24, 'swap outer bits to inner bits';
+        is swap_nibbles(0xfedc), 0xefcd, '16 bit';
+        is swap_nibbles(0xfedcba98), 0xefcdab89, '32 bit';
+        no warnings 'portable';
+        is swap_nibbles(0xfedcba9876543210), 0xefcdab8967452301, '64 bit';
+	}
+
+    done_testing;
+    exit;
+}