First a simple version, equivalent to yours but more readable.
(defmacro compile-instructions
[instructions]
(let [memory (gensym "memory-")]
`(fn [~memory]
~@(map (fn [[op m1 m2]]
`(aset ~memory ~m1 (~op (aget ~memory ~m1) (aget ~memory
~m2))))
instructions))))
(def memory (into-array Integer/TYPE (range 4)))
(def compiled (compile-instructions ([+ 2 3] [- 0 1] [+ 1 0])))
And another one to workaround the JVM 64K "feature". I split the generated
code into blocks of 500 instructions.
(def length-threshold 500)
(defmacro protected-fn [binding-form & body]
(if (<= (count body) length-threshold)
`(fn ~binding-form ~...@body)
(let [small-funs (partition length-threshold length-threshold ()
body)
let-block (map (fn [bod] (let [name (gensym "let-")] [name
`(fn [...@binding-form] ~@ bod)] )) small-funs)]
`(let [~@(apply concat let-block)]
(protected-fn [...@binding-form] ~@(map (fn [[name code]] `(~name
~...@binding-form)) let-block))))))
(defmacro compile-instructions-2
[instructions]
(let [memory (gensym "memory-")]
`(protected-fn [~memory]
~@(map (fn [[op m1 m2]]
`(aset ~memory ~m1 (~op (aget ~memory ~m1) (aget ~memory
~m2))))
instructions))))
(def compiled-2 (eval `(compile-instructions-2 ~(take 1150 (cycle '([+ 2 3]
[- 0 1] [+ 1 0]))))))
This last line is quite ugly. In fact, if you want to use
compile-instruction programatically, maybe it should not be a macro but a
function.
Then using a code-generating function in a macro is easy.
Plus, it is easy to eval the generated code.
But, be careful, you have to eval it once, just after the compiling phase.
Then, you get a real function.
eval is evil, but eval is not evil is a compiler (you have to evaluate the
code you read).
However eval is evil again in an "embedded compiler", when you use macro to
extend Clojure.
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