Example One

$$\langle \; \rangle \; x := 2*y \; \langle x = 2y \rangle$$

(where $x = \mathbb{R}$x$\mathbb{R}$) is totally correct, since if we replace $x$ by $E = 2y$ in $\alpha = \lq\lq (x=2y)''$ gives ``$(2y = 2y)$'' which is just True