A recursive sub is when a sub calls itself in some form.
The best example of this usually given is the mathematical function factorial (denoted by !). Are you familiar with it? 4! = 4*3*2*1. 7! = 7*6*5*4*3*2*1. In general, n! = n*(n-1)*(n-2)*...*2*1. But you could also say that n! = n*(n-1)!.
so if you would make a sub called factorial, then it would be something like this:
sub factorial {
my $n = shift;
return $n * &factorial( $n - 1 );
}
but this obviously doesn't work, 'cause it will keep going and going, so you need a stopping point too.
sub factorial {
my $n = shift;
if ( $n == 1 ) { return 1 }
return $n * &factorial( $n - 1 );
}
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