In Haskell:<br><br>&gt; let 2 + 2 = 5 in 2 + 2<br>==&gt; 5<br><br>(This works by locally defining a function named "+" since all infix operators is just syntactic sugar for function calls. This two-place function is well defined only for the inputs 2 and 2, in which case it returns 5. We can define a semantically equivalent expression as follows:)<br><br>&gt; let f(x, y) = if x == 2 &amp;&amp; y == 2 then 5 else undefined in f(2, 2)