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;;; Simple arithmetic expression compiler for jas in jas.
;;;
;;; The compiler is defined in the function
;;; compile-expression
;;;
;;; use as (for instance)
;;; (compile-expression (quote (+ (* 2 (+ 1 3)) 1)))
;;;
;;; This will generate a standalone program called results.class
;;; Run the bytecode interpreter on it as:
;;;
;;; % java results
;;;
;;; which will print the result of the expression
(define compile-expression
(lambda (expr)
(real-compile-expression expr)
(dump-code)))
;; The fun part...
(define real-compile-expression
(lambda (expr)
(cond
((num? expr)
(compile-number expr))
(1 (progn
(real-compile-expression (get-op1 expr))
(real-compile-expression (get-op2 expr))
(compile-op (get-op expr))
(set! cur-stack-height (- cur-stack-height 1)))))))
;; Ah well. Back to boring bookkeeping.
(define compile-number
(lambda (num)
(append-insn (bipush num))
(set! cur-stack-height (+ 1 cur-stack-height))
(cond
((< max-stack-height cur-stack-height)
(set! max-stack-height cur-stack-height)))))
(define compile-op
(lambda (op)
(cond
((eq? op (quote +)) (append-insn (iadd)))
((eq? op (quote -)) (append-insn (isub)))
((eq? op (quote *)) (append-insn (imul)))
((eq? op (quote /)) (append-insn (idiv))))))
(define get-op1
(lambda (expr) (car (cdr expr))))
(define get-op2
(lambda (expr) (car (cdr (cdr expr)))))
(define get-op
(lambda (expr) (car expr)))
(define append-insn
(lambda (insn)
(jas-code-addinsn my-code insn)))
(define cur-stack-height 1)
(define max-stack-height 1)
(define my-code (make-code))
(define my-init-code (make-code))
; define the main() portion,
; and the call to print out the
; results.
(define append-sequence
(lambda (code-part insn-list)
(mapcar (lambda (insn) (jas-code-addinsn code-part insn))
insn-list)))
(append-sequence
my-init-code
(quote
((aload_0)
(invokenonvirtual (make-method-cpe "java/lang/Object" "<init>" "()V"))
(return))))
(define dump-code
(lambda ()
(define my-env (make-class-env))
(jas-class-setclass my-env (make-class-cpe "results"))
(jas-class-setsuperclass my-env (make-class-cpe "java/lang/Object"))
(jas-class-addmethod my-env acc-public "<init>" "()V" my-init-code ())
(append-sequence
my-code
(quote
((getstatic
(make-field-cpe "java/lang/System" "out" "Ljava/io/PrintStream;"))
(swap)
(invokevirtual (make-method-cpe
"java/io/PrintStream" "println" "(I)V"))
(return))))
(jas-code-stack-size my-code max-stack-height)
(jas-class-addmethod my-env
(| acc-public acc-static)
"main" "([Ljava/lang/String;)V" my-code ())
(jas-class-write my-env
(make-outputstream "results.class"))))
;;;
;;; example usage of compiler.
;;;
;;; run the compiled class with
;;; % java results
;;; to get the answer.
(compile-expression (quote (+ (* 2 (+ 1 3)) 1)))
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