> Any language that is only pure is about as useful as write-only memory. That's actually not true -- you can write the core of a system in a pure language, th

> Any language that is only pure is about as useful as write-only memory. That's actually not true -- you can write the core of a system in a pure language, then use that pure core as a library in larger applications. Pure languages like Coq and Agda are often not Turing-complete, so various sorts of verification and proofs can be applied more easily.