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# File: AngularDifference.pm

...
}

1;

# File: AngularDifference.t

...
# multiples of 360-degrees shouldn't matter
my ($a,$b) = (360 * 2, 360 * 4);
is( angdiff($a,$b+23),23, "$a,$b+23 -> 23" );  # case 6

$ perl AngularDifference.t
1..6
...
#     expected: '90'
ok 6 - 720,1440+23 -> 23
# Looks like you failed 1 tests of 6.

sub angdiff($$) {
    my ($a, $b) = @_;
    return abs($a - $b) % 180;
}

$ perl AngularDifference.t
1..6
...
ok 4 - 45,0 -> 45
ok 5 - 0,270 -> 90, not 270
ok 6 - 720,1440+23 -> 23

is( angdiff( 90, 90),   0, "zero at 90" );   # case 2

# File: AngularDifference.l.t

...
    ##[ a <- Int, diff <- Int(range=>[-180,180]) ]##
    angdiff($a, $a + $diff) == abs($diff)
}, name => "angdiff holds to defn of angular difference";

    ##[ a <- Int, diff <- Int(range=>[-180,180]) ]##

    angdiff($a, $a + $diff) == abs($diff)

$ perl AngularDifference.l.t
1..1
...
# Counterexample:
# $a = 148;
# $diff = 180;

When $a = 0

...
  190           170             10  <-- Oops
  200           160             20  <-- Oops
  210           150             30  <-- Oops

sub angdiff($$) {
    my ($a, $b) = @_;
    my $delta = ($a - $b) % 360;
    return $delta > 180 ? 360 - $delta : $delta;
}

$ perl AngularDifference.l.t
1..1
ok 1 - 'angdiff holds to defn of angular difference' (1000 attempts)

Property {

...
    angdiff($a, $a + $diff) == abs($diff)

}, name => "angdiff holds to defn of angular difference";

1..1
ok 1 - 'angdiff holds to defn of angular difference' (1000 attempts)
#  58% 1 to 90
#  41% 91 to 180
#   0% zero

Property {

...
    angdiff($a, $b) == abs($diff)

}, name => "angdiff holds to defn of angular difference";

1..1
ok 1 - 'angdiff holds to defn of angular difference' (1000 attempts)
#  98% > 360
#   0% 181 to 360
#   0% 1 to 90

n <- OneOf( Int(range=>[-1,1]), Int )

Property {

...
    angdiff($a, $b) == abs($diff)

}, name => "angdiff holds to defn of angular difference";

1..1
ok 1 - 'angdiff holds to defn of angular difference' (1000 attempts)
...
#   9% 1 to 90
#   6% 91 to 180
#   0% zero

n <- Frequency( [20,Int(range=>[-1,1])], [1,Int] )

1..1
ok 1 - 'angdiff holds to defn of angular difference' (1000 attempts)
...
#  18% 1 to 90
#  10% 91 to 180
#   0% zero