\dvips \usepackage[nohug]{diagrams} \diagram{ \mathbb N & \rDashto^{\tt upFrom} & {\tt Stream}_{\mathbb N} \\ \dTo^{\langle 1_{\mathbb N}, {\tt succ}\rangle} & & \dTo_{\langle{\tt head}, {\tt tail}\rangle} \\ \mathbb N \times \mathbb N & \rTo & \mathbb N \times {\tt Stream}_{\mathbb N} }