On Thursday, October 25, 2012 11:44:50 AM UTC-7, Jim foo.bar wrote: > > On 25/10/12 19:38, Brian Craft wrote: > > Multimethods seem like a convenience layer over duck typing: probe the > object to see what it is, then dispatch. Is that a fair description? > > > Not exactly...MUlti-methods have no limitations with regarding dispatch. > You can dispatch on anything...I mean ANYTHING!!! To give you an idea, my > canva-react mulit-method dispatches on the type of game being played at the > moment which is not part of the parameters passed in!!! In other words the > dispatch function completely ignores the arguments! Nothing to do with > types/classes etc etc. You dispatch on some function - that is it!!! > > similarly: > > (defmulti halt > (fn [_ _] ;dispatch-function checks for OS - ignores args > (let [os (System/getProperty "os.name")] > (if (.startsWith os "Mac OS") :Linux (keyword os))))) > > ;;for Linux and Mac machines > (defmethod halt :Linux [root-pwd minutes-after] > (clojure.java.shell/sh > "sudo" "-S" "shutdown" (str "+" minutes-after) :in (str root-pwd "\n")) > ) > > ;;for Windows machines > (defmethod halt :Windows [_ minutes-after] > (clojure.java.shell/sh "shutdown" "-s" "-t" (str minutes-after))) > > ;;for Solaris machines > (defmethod halt :Solaris [root-pwd seconds-after] > (clojure.java.shell/sh > "shutdown" "-S" "-y" (str "-g" seconds-after) "-i" "S" :in (str > root-pwd "\n"))) > > ;;in case nothing fires > (defmethod halt :default [] (throw (UnsupportedOperationException. > "Unsupported > operating system!"))) > > heh. I see. Thanks!
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