+ my ($r2, $l2) = $self->inspect($op->sibling);
+ return $r2, $l2 if $r2 and zero $l2;
+ my $c2 = count $l2; # First one to happen
+
+ my ($r1, $l1) = $self->inspect($op);
+ return (add $r2, scale $c2, $r1), undef if $r1 and zero $l1 and not zero $l2;
+ diag Dumper [ [ $r1, $l1 ], [ $r2, $l2 ] ] if $DEBUG;
+ my $c1 = count $l1;
+
+ $l2 = { $l2 => 1 } unless ref $l2;
+ my $r = add $r2,
+ scale $c2,
+ add map { scale $l2->{$_}, cumulate $r1, $_, $c1 } keys %$l2;
+ my $c = 1 - count $r;
+ my $l = scale $c, normalize add map { power $l1, $_, $l2->{$_} } keys %$l2;
+ return $r, $l;