Line circle intersection: Difference between revisions

=={{header|Perl}}==

<lang perl>use strict;

use warnings;

use feature 'say';

use List::Util 'sum';

sub find_intersection {

my($P1, $P2, $center, $radius) = @_;

my @d = ($$P2[0] - $$P1[0], $$P2[1] - $$P1[1]);

my @f = ($$P1[0] - $$center[0], $$P1[1] - $$center[1]);

my $a = sum map { $_**2 } @d;

my $b = 2 * ($f[0]*$d[0] + $f[1]*$d[1]);

my $c = sum(map { $_**2 } @f) - $radius**2;

my $D = $b**2 - (4*$a*$c);

return unless $D >= 0;

my ($t1,$t2) = ((-$b - sqrt($D))/(2*$a), (-$b + sqrt($D))/(2*$a));

return unless ( $t1 >= 0 and $t1 <= 1 ) or ( $t2 >= 0 and $t2 <= 1 );

my ($dx, $dy) = ($$P2[0] - $$P1[0], $$P2[1] - $$P1[1]);

return ([$dx*$t1 + $$P1[0], $dy*$t1 + $$P1[1]],

[$dx*$t2 + $$P1[0], $dy*$t2 + $$P1[1]])

}

my @data = (

[ [-10, 11], [ 10, -9], [3, -5], 3 ],

[ [-10, 11], [-11, 12], [3, -5], 3 ],

[ [ 3, -2], [ 7, -2], [3, -5], 3 ],

[ [ 3, -2], [ 7, -2], [0, 0], 4 ],

[ [ 0, -3], [ 0, 6], [0, 0], 4 ],

[ [ 6, 3], [ 10, 7], [4, 2], 5 ],

[ [ 7, 4], [ 11, 18], [4, 2], 5 ],

);

sub rnd { map { (sprintf('%.2f', $_)) =~ s/\.00//r } @_ }

for my $d (@data) {

my @solution = find_intersection(@$d[0] , @$d[1] , @$d[2], @$d[3]);

say 'For input: ' . join(', ', (map { '('. join(',', @$_) .')' } @$d[0,1,2]), @$d[3]);

say 'Solutions: ' . (@solution > 1 ? join ', ', map { '('. join(',', rnd(@$_)) .')' } @solution : "None");

say '';

}</lang>

{{out}}

<pre>For input: (-10,11), (10,-9), (3,-5), 3

Solutions: (3,-2), (6,-5)

For input: (-10,11), (-11,12), (3,-5), 3

Solutions: None

For input: (3,-2), (7,-2), (3,-5), 3

Solutions: (3,-2), (3,-2)

For input: (3,-2), (7,-2), (0,0), 4

Solutions: (-3.46,-2), (3.46,-2)

For input: (0,-3), (0,6), (0,0), 4

Solutions: (0,-4), (0,4)

For input: (6,3), (10,7), (4,2), 5

Solutions: (1,-2), (8,5)

For input: (7,4), (11,18), (4,2), 5

Solutions: (5.03,-2.89), (7.46,5.61)</pre>