sub fibonacci { my ($visitor) = @_; my ($i, $j) = (0, 1); $visitor->() for $i; for (;;) { $visitor->() for $j; ($i, $j) = ($j, $i+$j); } } #### sub fibonacci { my ($visitor) = @_; my ($i, $j) = (0, 1); $visitor->() for $i; _fibonacci($i, $j); } sub _fibonacci { my ($visitor, $i, $j) = @_; $visitor->() for $j; _fibonacci($j, $i+$j); } #### sub fibonacci { my ($i, $j) = (0, 1); return ( \$i, sub { _fibonacci($i, $j) } ); } sub _fibonacci { my ($i, $j) = @_; return ( \$j, sub { _fibonacci($j, $i+$j) } ); } #### { my $iter = make_iter(\&fibonacci); for (0..15) { my ($n) = $iter->() or last; print("$n "); } print("\n"); } #### 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610