If you only want to look at functional a more pure functional language like haskell may fit yyou better both ocaml and F# allows to do functions which are not t

If you only want to look at functional a more pure functional language like haskell may fit yyou better both ocaml and F# allows to do functions which are not truly pure it even have mutable variables which are not normally a thing. So if it to learn purely functional haskell or SML may be better.