Solver CARTOON (animation) that multiplies signed numbers

Source code of 'CARTOON (animation) that multiplies signed numbers'

This Solver (CARTOON (animation) that multiplies signed numbers) was created by by ichudov(507)

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==section input
Multiply *[input a=3] and *[input b=-2].

==section solution
perl

print "This solver follows my lesson <A HREF=/algebra/homework/multiplication-of-signed-numbers/HOW-TO-multiply-negatives.lesson>HOW TO multiply negatives</A>.";

$prod = $a*$b;

print "Solve: {{{$a*$b}}}\n\n\n";

if( $a >= 0 && $b >= 0 ) {
    print "Both $a and $b are not negative, so, the problem simply solves by multiplying them:

$a*$b=$prod.";
} elsif( $a < 0 && $b >= 0 ) {
  my $oppa = -$a;
    print "We are multiplying a NEGATIVE number $a by a POSITIVE number $b. According to the lesson, we need to multiply the opposite of $a ($oppa) by $b, and take a negative of that:

{{{($a)*$b = -($oppa*$b) = $prod}}}

{{{ cartoon( ($a)*$b, -($oppa*$b), $prod ) }}}

";
} elsif( $a >= 0 && $b < 0 ) {
  my $oppb = -$b;
    print "We are multiplying a POSITIVE number $a by a NEGATIVE number $b. According to the lesson, we need to multiply $a by the opposite of $b ($oppb), and take a negative of that:

{{{$a*($b) = -($a*$oppb) = $prod}}}

{{{ cartoon( $a*$b, -($a*$oppb), $prod ) }}}
";
} elsif( $a < 0 && $b < 0 ) {
  my $oppa = -$a;
  my $oppb = -$b;
    print "We are multiplying a NEGATIVE number $a by a NEGATIVE number $b. According to the lesson, we need to multiply the opposite of $a ($oppa) by the opposite of $b ($oppb), that would give us the product of ($a)*($b):

{{{($a)*($b) = $oppa*$oppb = $prod}}}
{{{ cartoon( ($a)*($b), $oppa*$oppb, $prod ) }}}

";
}
==section output
prod

==section check
  a=3 b=-2 prod=-6