Add some documentation to the abi

[scheme.git] / ast.scm

diff --git a/ast.scm b/ast.scm
index 19dc7a0f5d3bea33793e1de676016be618baa103..a0899192e21a1d44b0fe3296e380604133a3f1d2 100644 (file)
--- a/ast.scm
+++ b/ast.scm
@@ -1,11 +1,38 @@
-(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 let-bindings cadr)
 (define let-body cddr)
@@ -13,8 +40,8 @@
 (define (lambda? x)
   (and (list? x) (eq? (car x) 'lambda)))
 
-(define lambda-arg cadr)
-(define lambda-body cddr)
-
-(define (var? x)
-  (and (not (list? x)) (symbol? x)))
+; for use in normalized form
+(define lambda-arg caadr)
+; for use elsewhere
+(define lambda-args cadr)
+(define lambda-body caddr)