math.pl

use PDF::Haru;
use strict;
use warnings;

# create new document
my $pdf = PDF::Haru::New();
#$pdf->LoadTTFontFromFile("/usr/share/fonts/truetype/msttcorefonts/arial.ttf",1);
# add page
my $page = $pdf->AddPage();
# set page size and orientation
$page->SetSize(HPDF_PAGE_SIZE_A4, HPDF_PAGE_PORTRAIT);
my $font = $pdf->GetFont("Helvetica", "StandardEncoding");
$page->SetFontAndSize($font, 24);

my $page_width     = $page->GetWidth();
my $page_height    = $page->GetHeight();
my $zero_width     = $page->TextWidth("0");
my $template_width = $page->TextWidth("0" x 6);

sub one_equation {
	my ($x, $y) = @_;
	my $sign = ("-", "+")[rand 2];
	my ($a, $b);
	if ($sign eq "-") {
		$a = 1 + int rand 20;
		$b = 1 + int rand $a - 1;
	} else {
		$a = 1 + int rand 19;
		$b = 1 + int rand 18 - $a;
	}
	my $text = "$a $sign $b";
	my $tw   = $page->TextWidth($text);
	my $xo   = ($template_width - $tw) / 2;
	$page->BeginText();
	$page->TextOut($x + $xo,             $y, $text);
	$page->TextOut($x + $template_width, $y, "=");
	$page->EndText();
}

for (my $x = 0; $x < $page_width; $x += int($page_width / 3)) {
	for (my $y = 30; $y < $page_height - $page_height / 20; $y += int $page_height / 20) {
		one_equation($x, $y);
	}
}

# save the document to a file
$pdf->SaveToFile("filename.pdf");

# cleanup
$pdf->Free();