Composition of partial functions
= Composition of partial functions
Composition of <partial functions> is strict: $g(h_1(x),\ldots,h_r(x))$ is defined only if every $h_i(x)$ is defined and $g$ is defined on the resulting tuple. An argument discarded by the outer function still has to be defined. A representation in a non-strict programming language therefore needs an explicit sequencing guard.