Hello,
Consider the following code
(gen-interface
:name IntStack
:methods [[stackPeek [] int]
[stackPush [int] void]
[stackPop [] int]
[stackDepth [] int]])
(deftype IntStackImpl
[^{:tag ints :unsynchronized-mutable true} data
^{:tag int :unsynchronized-mutable true} depth]
IntStack
(stackPeek [this]
(aget data depth))
(stackPush [this value]
(when (>= (inc depth) (alength data))
(let [data-length (alength data)
new-data (int-array (* data-length 2))]
(System/arraycopy data 0 new-data 0 data-length)
(set! data new-data)))
(set! depth (inc depth))
(aset data depth value))
(stackPop [this]
(if (> depth 0)
(let [value (aget data depth)]
(set! depth (dec depth))
value)
(throw (IllegalStateException. "Stack is already empty!"))))
(stackDepth [this]
depth))
This is very simple stack implementation over plain java array. It does not
compile with the following message:
CompilerException java.lang.VerifyError: (class:
clojure/data/xml/IntStackImpl, method: stackPop signature: ()I) Expecting
to find integer on stack
However, when I replace the body of stackPop with, say, plain zero literal
0, the method seems to pass the compilation, because then I'm getting
similar error on stackPush method instead.
Placing type hints inside stackPop method does not work (in fact, it is
even an error to place them, say, on value local binding).
What am I doing wrong here? How to make the class compile?
Cheers,
Vladimir.
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