Merge pull request #4466 from jo-37/contrib

Solutions to challenge 120

2 files changed, 149 insertions, 0 deletions

diff --git a/challenge-120/jo-37/perl/ch-1.pl b/challenge-120/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..ca6f560789
--- /dev/null
+++ b/challenge-120/jo-37/perl/ch-1.pl
@@ -0,0 +1,67 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [N...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N...
+    number(s)
+
+EOS
+
+
+### Input and Output
+
+say swap_bits($_) for @ARGV;
+
+
+### Implementation
+
+sub swap_bits ($n) {
+    no warnings 'portable';
+    # Set $odd to a mask with all odd bits set in the maximum internal
+    # representation.
+    # Oops! There was a restriction to N < 256 again.  Realized it only
+    # after the full-size solution had been finished.
+    state $odd = hex 5 x ((unpack '%b*', pack 'j', -1) / 4);
+
+    # Right-shift even bits and left-shift odd bits.
+    ($n & ($odd << 1)) >> 1 | ($n & $odd) << 1;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is swap_bits(101), 154, 'example 1';
+        is swap_bits(18), 33, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is swap_bits(0), 0, 'no bit set';
+        is swap_bits(~0), ~0, 'all bits set';
+        is swap_bits(0x55555555), 0xaaaaaaaa, 'odd to even';
+        is swap_bits(0xaaaaaaaa), 0x55555555, 'even to odd';
+	}
+
+    done_testing;
+    exit;
+}
diff --git a/challenge-120/jo-37/perl/ch-2.pl b/challenge-120/jo-37/perl/ch-2.pl
new file mode 100755
index 0000000000..2ee102cb6d
--- /dev/null
+++ b/challenge-120/jo-37/perl/ch-2.pl
@@ -0,0 +1,82 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [time...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+time...
+    calculate the smaller angle between hour and minute hands for the
+    given time(s).
+
+EOS
+
+
+### Input and Output
+
+say clock_angle($_) // "invalid time: $_" for @ARGV;
+
+
+### Implementation
+
+# To find the smaller angle between the hands we need a "double
+# triangular" function in the range (-2m, 2m) with this shape:
+#
+# m     /\      /\
+#      /  \    /  \
+#     /    \  /    \
+# 0  /      \/      \
+#  -2m  -m  0   m   2m
+#
+# which is provided by: f(x) = m - abs(m - abs(x))
+#
+# The minute and hour hands move 6° and 0.5° per minute respectively,
+# resulting in a difference of 5.5° per minute.
+
+sub clock_angle ($time) {
+    # The accepted time format is [H]H:MM.  Distinguishing between
+    # invalid time strings and a zero degree angle.
+    $time =~ /^([01]?\d|2[0-3]):([0-5]\d)$/ || undef and
+        180 - abs 180 - abs $1 % 12 * 30 - 5.5 * $2;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is clock_angle('03:10'), 35, 'example 1';
+        is clock_angle('04:00'), 120, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is clock_angle(12345), U(), 'not a valid time';
+        is clock_angle('25:00'), U(), 'not a valid hour';
+        is clock_angle('23:60'), U(), 'not a valid minute';
+        is clock_angle('0:00'), 0, 'omit leading zero';
+        is clock_angle('12:00'), 0, 'zero degrees';
+        is clock_angle('5:00'), 150, 'min to hour';
+        is clock_angle('7:00'), 150, 'hour to min';
+        # The smallest angles besides noon and midnight:
+        is clock_angle($_), 0.5, $_ for (qw(2:11 9:49 14:11 21:49));
+	}
+
+    done_testing;
+    exit;
+}