Functional language for smart contracts?

[Slava79]

Is there a functional approach to writing smart contracts? Any cryptocurrency having or planning to implement it?

Got interested in it after reading about all the disasters happened in this area.

In my opinion, writing smart contracts code in the form of pure functions would drastically reduce the space of potential errors and increased testability.

I tried to google it but without big success, found only this https://www.fstar-lang.org/ which is close but not exactly what I meant.