Useful when you want to provide several implementations of the same
protocol all at once. Takes a single protocol and the implementation
of that protocol for one or more types. Expands into calls to
extend-type:
(extend-protocol Protocol
AType
(foo [x] ...)
(bar [x y] ...)
BType
(foo [x] ...)
(bar [x y] ...)
AClass
(foo [x] ...)
(bar [x y] ...)
nil
(foo [x] ...)
(bar [x y] ...))
expands into:
(do
(clojure.core/extend-type AType Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type BType Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type AClass Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type nil Protocol
(foo [x] ...)
(bar [x y] ...)))