;; 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
;; 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,
(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))
HCoop / bpt / guile.git / commitdiff