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#!/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;
}
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