You are correct that the semantics (meaning) of subroutines in pure functional languages resembles mathematical functions more than their semantics in imperativ

You are correct that the semantics (meaning) of subroutines in pure functional languages resembles mathematical functions more than their semantics in imperative languages (which is a different mathematical object [1]). But so what? [1]: https://en.wikipedia.org/wiki/Predicate_transformer_semantics https://en.wikipedia.org/wiki/Predicate_transformer_semantic...