  We show that if $L$ is a topological vector lattice, $u \colon L \to L$ is
the function $u(x) = x \vee 0$, $C \subset L$ is convex, and $D = u(C)$ is
metrizable, then $D$ is an ANR and $u|_C \colon C \to D$ is a homotopy
equivalence and thus an AR. This is proved by verifying the hypotheses of a
second result: if $X$ is a connected space that is homotopy equivalent to an
ANR, $Y$ is an ANR, and $f \colon X \to Y$ is a continuous surjection such that
for each $y \in Y$ and each neighborhood $V \subset Y$ of $y$, there is a
neighborhood $V' \subset V$ of $y$ such that $f^{-1}(V')$ can be contracted in
$f^{-1}(V)$, then $f$ is a homotopy equivalence. The latter result is a
geometric analogue of the Vietoris-Begle theorem.
