@defun "diff2" {
	"y2" store
	"x2" store
	"y1" store
	"x1" store
	x1 x2 -
	y1 y2 -
}

@defun "dup2" {
	"b" store
	"a" store
	a b a b
}

@defun "swap2" {
	"b2" store
	"b1" store
	"a2" store
	"a1" store
	b1 b2 a1 a2
}