Example:Empty codomain function

It is impossible to define a function [math]f : A \href{/cs2800/wiki/index.php/%E2%86%92}{→} \href{/cs2800/wiki/index.php/%E2%88%85}{∅} [/math] for any (non-empty) set A. Indeed, if there exists an element [math]x \href{/cs2800/wiki/index.php/%E2%88%88}{∈} A [/math], then [math]f(x) [/math] cannot be in ∅, so [math]f [/math] cannot be well-defined.