AFAICT having fmap dispatch on the type of the second argument makes it practically impossible to define fmap for arbitrary functions, since the type is different for each function:

user> (type type)
clojure.core$type
user> (type fn?)
clojure.core$fn_QMARK_
user> (type not=)
clojure.core$not_EQ_
user>

However, there's a perfectly reasonable definition of fmap for functions (fmap = comp).

To my mind the simplest/best thing to do is just have a Functor protocol and have fmap call a function in it, with the order of arguments reversed so that dispatch will happen correctly.

All algo.generic submodules except for functor are mentioned in the README.

Attached is a patch that rectifies this.