-(define (app? x)
- (and (list? x)
- (>= (length x) 2)
- (not (eq? (car x) 'let))
- (not (eq? (car x) 'lambda))))
+(define (ast-type x)
+ (define (builtin? x)
+ (case x
+ ('+ #t)
+ ('- #t)
+ ('* #t)
+ ('! #t)
+ ('= #t)
+ ('bool->int #t)
+ ('print #t)
+ (else #f)))
+ (cond
+ ((list? x)
+ (case (car x)
+ ('if 'if)
+ ('let 'let)
+ ('lambda 'lambda)
+ ('closure 'closure) ; only available in codegen
+ ('static-string 'static-string) ; only available in codegen
+ (else 'app)))
+ ((builtin? x) 'builtin)
+ ((symbol? x) 'var)
+ ((integer? x) 'int-literal)
+ ((boolean? x) 'bool-literal)
+ ((string? x) 'string-literal)))
-(define (let? x)
- (and (list? x) (eq? (car x) 'let)))
+(define (ast-traverse f x)
+ (case (ast-type x)
+ ('let `(let ,(map (lambda (x) (list (car x) (f (cadr x))))
+ (let-bindings x))
+ ,@(map f (let-body x))))
+ ('app (map f x))
+ ('lambda `(lambda ,(lambda-args x) ,(f (lambda-body x))))
+ ('if `(if ,@(map f (cdr x))))
+ (else x)))
+
+(define (ast-collect f x)
+ (define (inner y) (ast-collect f y))
+ (case (ast-type x)
+ ['let (append (f x)
+ (fold-map inner (let-bindings x))
+ (fold-map inner (let-body x)))]
+ ['app (append (f x)
+ (fold-map inner x))]
+ ['lambda (append (f x)
+ (inner (lambda-body x)))]
+ ['if (append (f x)
+ (fold-map inner (cdr x)))]
+ [else (f x)]))
(define let-bindings cadr)
(define let-body cddr)
(define lambda-args cadr)
(define lambda-body caddr)
-(define (var? x)
- (and (not (list? x)) (symbol? x)))
+; utils
+(define (fold-map f x) (fold-left append '() (map f x)))
+(define (repeat x n) (if (<= n 0) '()
+ (cons x (repeat x (- n 1)))))
-(define (builtin? x)
- (case x
- ('+ #t)
- ('- #t)
- ('* #t)
- ('! #t)
- ('bool->int #t)
- (else #f)))
+
+(define-syntax push!
+ (syntax-rules ()
+ ((_ s x) (set! s (cons x s)))))
+
+(define-syntax pop!
+ (syntax-rules ()
+ ((_ s) (let ([x (car s)])
+ (set! s (cdr s))
+ x))))