The Truth

Lisp (scheme, common lisp) and C is all you need.

Try to prove me wrong.

computation is a temporal physical process happening in computer memory
wants to describe computation using expressions with non-temporal, non-physical algebraic semantics that enable equational reasoning

Aren't you the faglord. Even your fucking Agda or Mercury

pureFunction 5

will cause temporary physical effects in computer memory during its execution. If things could be kept purely denotational and algebraic, then we wouldn't need computers.