Curve that touches three points: Difference between revisions

=={{header|Perl}}==

Hilbert '''curve''' task code repeated here, with the addition that the 3 task-required points are marked. Mostly satisfies the letter-of-the-law of task specification while (all in good fun) subverting the spirit of the thing.

<lang perl>use SVG;

use List::Util qw(max min);

use constant pi => 2 * atan2(1, 0);

# Compute the curve with a Lindemayer-system

%rules = (

A => '-BF+AFA+FB-',

B => '+AF-BFB-FA+'

);

$hilbert = 'A';

$hilbert =~ s/([AB])/$rules{$1}/eg for 1..6;

# Draw the curve in SVG

($x, $y) = (0, 0);

$theta = pi/2;

$r = 5;

for (split //, $hilbert) {

if (/F/) {

push @X, sprintf "%.0f", $x;

push @Y, sprintf "%.0f", $y;

$x += $r * cos($theta);

$y += $r * sin($theta);

}

elsif (/\+/) { $theta += pi/2; }

elsif (/\-/) { $theta -= pi/2; }

}

$max = max(@X,@Y);

$xt = -min(@X)+10;

$yt = -min(@Y)+10;

$svg = SVG->new(width=>$max+20, height=>$max+20);

$points = $svg->get_path(x=>\@X, y=>\@Y, -type=>'polyline');

$svg->rect(width=>"100%", height=>"100%", style=>{'fill'=>'black'});

$svg->polyline(%$points, style=>{'stroke'=>'orange', 'stroke-width'=>1}, transform=>"translate($xt,$yt)");

my $task = $svg->group( id => 'task-points', style => { stroke => 'red', fill => 'red' },);

$task->circle( cx => 10, cy => 10, r => 1, id => 'point1' );

$task->circle( cx => 100, cy => 200, r => 1, id => 'point2' );

$task->circle( cx => 200, cy => 10, r => 1, id => 'point3' );

open $fh, '>', 'curve-3-points.svg';

print $fh $svg->xmlify(-namespace=>'svg');

close $fh;</lang>

[https://github.com/SqrtNegInf/Rosettacode-Perl5-Smoke/blob/master/ref/curve-3-points.svg Hilbert curve passing through 3 defined points] (offsite image)