Hi everyone,
here is an odd one for you...I've got this tiny protocol:
(defprotocol Normalisable
(normalise [this transform-fn]
[this transform-fn limits]))
now, I'd like to have it extended to clojure native data-structures; no
problem:
(extend-protocol Normalisable
java.lang.Number
(normalise
([this transform] (normalise this transform [10 -10 1 -1]))
([this transform limits] (apply transform this limits)))
clojure.lang.IPersistentVector
(normalise
([this transform]
(let [top (apply max this)
bottom (apply min this)]
(mapv #(normalise % transform [top bottom]) this)) )
([this transform limits]
(normalise this #(transform % limits))) )
clojure.lang.IPersistentSet
(normalise
([this transform]
(let [top (apply max this)
bottom (apply min this)]
(persistent!
(reduce #(conj! %1 (normalise %2 transform [top bottom])) (transient
#{}) this))))
([this transform limits]
(normalise this #(transform %1 %2 %3 (first limits) (second limits)))) )
)
So far so good...now I'd like to have it extended to arrays. I added the
following to my 'extend-protocol' form:
(Class/forName "[D")
(normalise
([this transform]
(let [top (apply max this)
bottom (apply min this)]
(amap ^doubles this idx ret (normalise (aget ^doubles this idx)
transform [top bottom]))))
([this transform limits]
(normalise this #(transform % limits))))
and this throws this where the 'extend-protocol' form starts:
CompilerException java.lang.UnsupportedOperationException: nth not
supported on this type: *Character*, compiling: (line 27)
if I replace (Class/forName "[D") with (class (double-array 1)) the
error is slightly different:
CompilerException java.lang.UnsupportedOperationException: nth not
supported on this type: *Symbol*, compiling: (line 27)
what on earth is going on? What character and what symbol is the error
referring to? And where is nth being called?
the stack trace is the following but it's not very helpful (at least
not to me!):
Compiler.java:6380 clojure.lang.Compiler.analyze
Compiler.java:6322 clojure.lang.Compiler.analyze
Compiler.java:2879 clojure.lang.Compiler$MapExpr.parse
Compiler.java:6369 clojure.lang.Compiler.analyze
Compiler.java:6322 clojure.lang.Compiler.analyze
Compiler.java:3624 clojure.lang.Compiler$InvokeExpr.parse
Compiler.java:6562 clojure.lang.Compiler.analyzeSeq
Compiler.java:6361 clojure.lang.Compiler.analyze
Compiler.java:6322 clojure.lang.Compiler.analyze
Compiler.java:5708
clojure.lang.Compiler$BodyExpr$Parser.parse
Compiler.java:5139 clojure.lang.Compiler$FnMethod.parse
Compiler.java:3751 clojure.lang.Compiler$FnExpr.parse
Compiler.java:6558 clojure.lang.Compiler.analyzeSeq
Compiler.java:6361 clojure.lang.Compiler.analyze
Compiler.java:6616 clojure.lang.Compiler.eval
Compiler.java:6608 clojure.lang.Compiler.eval
Compiler.java:7064 clojure.lang.Compiler.load
Compiler.java:7020 clojure.lang.Compiler.loadFile
RT.java:318 clojure.lang.RT$3.invoke
NO_SOURCE_FILE:1 user/eval252
Compiler.java:6619 clojure.lang.Compiler.eval
Compiler.java:6582 clojure.lang.Compiler.eval
core.clj:2852 clojure.core/eval
main.clj:259 clojure.main/repl[fn]
main.clj:259 clojure.main/repl[fn]
main.clj:277 clojure.main/repl[fn]
main.clj:277 clojure.main/repl
RestFn.java:1096 clojure.lang.RestFn.invoke
interruptible_eval.clj:56
clojure.tools.nrepl.middleware.interruptible-eval/evaluate[fn]
AFn.java:159 clojure.lang.AFn.applyToHelper
AFn.java:151 clojure.lang.AFn.applyTo
core.clj:617 clojure.core/apply
core.clj:1788 clojure.core/with-bindings*
RestFn.java:425 clojure.lang.RestFn.invoke
interruptible_eval.clj:41
clojure.tools.nrepl.middleware.interruptible-eval/evaluate
interruptible_eval.clj:171
clojure.tools.nrepl.middleware.interruptible-eval/interruptible-eval[fn]
core.clj:2330 clojure.core/comp[fn]
interruptible_eval.clj:138
clojure.tools.nrepl.middleware.interruptible-eval/run-next[fn]
AFn.java:24 clojure.lang.AFn.run
ThreadPoolExecutor.java:1145
java.util.concurrent.ThreadPoolExecutor.runWorker
ThreadPoolExecutor.java:615
java.util.concurrent.ThreadPoolExecutor$Worker.run
Thread.java:722 java.lang.Thread.run
Caused by: java.lang.UnsupportedOperationException: nth not supported on
this type: Character
RT.java:857 clojure.lang.RT.nthFrom
RT.java:807 clojure.lang.RT.nth
core_deftype.clj:758 clojure.core/emit-hinted-impl[fn]
core.clj:2487 clojure.core/map[fn]
LazySeq.java:42 clojure.lang.LazySeq.sval
LazySeq.java:60 clojure.lang.LazySeq.seq
RT.java:484 clojure.lang.RT.seq
RT.java:537 clojure.lang.RT.countFrom
RT.java:530 clojure.lang.RT.count
Cons.java:49 clojure.lang.Cons.count
Compiler.java:6352 clojure.lang.Compiler.analyze
can anyone help with this? the thing that drives me crazy is the fact
that if I do the following in a separate namespace, it compiles just fine!
(defprotocol FOO
(bar [this a] [this a b]))
(extend-protocol FOO
(Class/forName "[D")
(bar
([this a] 1)
([this transform limits] 2)))
thanks in advance :)
Jim
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