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remove lambda wrap hack of brainfuck tree-il compiler

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* module/language/brainfuck/compile-tree-il.scm (compile-tree-il):
  Remove the hack where we wrapped the compiled code in a `lambda',
  because not only should the tree-il compiler optimize that away, it
  was really papering around other inefficiencies, and obtuse to boot.
This commit is contained in:
Andy Wingo 2009-06-24 13:42:59 +02:00
parent 0ebbcf43c4
commit a84673a68b
1 changed files with 5 additions and 18 deletions
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23
module/language/brainfuck/compile-tree-il.scm
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@ -49,12 +49,11 @@
;; This compiles a whole brainfuck program. This constructs a Tree-IL
;; code equivalent to Scheme code like this:
;;
;; ((lambda ()
;; (let ((pointer 0)
;; (tape (make-vector tape-size 0)))
;; (begin
;; <body>
;; (write-char #\newline)))))
;; (write-char #\newline)))
;;
;; So first the pointer and tape variables are set up correctly, then the
;; program's body is executed in this context, and finally we output an
@ -69,17 +68,6 @@
;; throw an error, whereas a number of Brainfuck compilers do not detect
;; this.
;;
;; We wrap the code in a lambda so that the body has a place to cache
;; the looked-up locations of the primitive functions: vector-ref et al.
;; This way we can use toplevel-ref instead of link-now + variable-ref.
;; See the VM documentation for more info on those instructions.
;;
;; Normally when compiling you don't have to think about this at all,
;; because the usual pattern is a bunch of definitions, then you call
;; those definitions -- so the real work is in the functions anyway,
;; which can use toplevel-ref. Here we just force that pattern into
;; effect.
;;
;; Note that we're generating the S-expression representation of
;; Tree-IL, then using parse-tree-il to turn it into the actual Tree-IL
;; data structures. This makes the compiler more pleasant to look at,
@ -104,11 +92,10 @@
(define (compile-tree-il exp env opts)
(values
(parse-tree-il
`(apply (lambda () ()
(let (pointer tape) (pointer tape)
((const 0)
(apply (primitive make-vector) (const ,tape-size) (const 0)))
,(compile-body exp)))))
`(let (pointer tape) (pointer tape)
((const 0)
(apply (primitive make-vector) (const ,tape-size) (const 0)))
,(compile-body exp)))
env
env))