On 21 Mar 2010, at 20:34, Fogus wrote:
(defmethod clojure.core/print-method ::Piece [piece writer] ???what
goes
here???)
(defmethod clojure.core/print-method ::Piece
[piece writer]
(.write writer (str (:number piece) (:letter piece)) 0 2))
Extending Piece to provide a str method can replace that ugly bit in
the middle.
One more thing to know about print-method for deftype: The deftype
macro generates a default implementation for deftype. Defining your
own replaces the default version, which in most situations is just fine.
However, there is a situation that requires more effort. Suppose you
have a family of types for which you want to implement a common print-
method. The obvious approach for any multimethod would be to declare
all those types as derived from some parent (a namespace-qualified
keyword will do, there is no need to have any implementation for a
parent type) and have a print-method implementation for the parent.
The problem is just that the type's default implementation will be
used in preference to the shared one. The solution is to remove the
default method using remove-method.
Konrad.
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