X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=ast.scm;h=cfd774a2202cd5af24ae71c7facfd81bd966d63c;hp=5064ca554bc8033bdbc0b483ac79249cd3312f73;hb=HEAD;hpb=844dcd052c6f551d9936693c2b4c49cf920c7051

diff --git a/ast.scm b/ast.scm
index 5064ca5..cfd774a 100644
--- a/ast.scm
+++ b/ast.scm
@@ -1,3 +1,5 @@
+(load "utils.scm")
+
 (define (ast-type x)
   (define (builtin? x)
     (case x
@@ -15,13 +17,14 @@
       ('if 'if)
       ('let 'let)
       ('lambda 'lambda)
+      ('case 'case)
       ('closure 'closure) ; only available in codegen
       ('static-string 'static-string) ; only available in codegen
+      ('stack 'stack) ; only available in codegen (tag that value is passed via stack)
       (else 'app)))
    ((builtin? x) 'builtin)
    ((symbol? x) 'var)
    ((integer? x) 'int-literal)
-   ((boolean? x) 'bool-literal)
    ((string? x) 'string-literal)))
 
 (define (ast-traverse f x)
@@ -32,6 +35,11 @@
     ('app (map f x))
     ('lambda `(lambda ,(lambda-args x) ,(f (lambda-body x))))
     ('if `(if ,@(map f (cdr x))))
+    ('case `(case ,(f (case-switch x))
+	      ,@(map (lambda (x)
+		       (list (car x) (f (cadr x))))
+		     (case-cases x))))
+    ('stack `(stack ,(cadr x) ,(f (caddr x))))
     (else x)))
 
 (define (ast-collect f x)
@@ -46,47 +54,158 @@
 		     (inner (lambda-body x)))]
     ['if (append (f x)
 		 (flat-map inner (cdr x)))]
+    ['case (append (f x)
+		   (inner (case-switch x))
+		   (flat-map inner (map cadr (case-cases x))))]
+    ['stack (append (f x)
+		    (inner (caddr x)))]
     [else (f x)]))
 
 (define (ast-find p x)
   (define (inner y) (ast-find p y))
-  (define (any p x) (fold-left
-		     (lambda (acc y) (if acc #t (p y)))
-		     #f
-		     x))
-  (define (either . fs)
-    (if (null? fs) #f
-	(if (car fs) (car fs)
-	    (apply either (cdr fs)))))
   
   (case (ast-type x)
-    ['let (either (p x)
+    ['let (or (p x)
 	      (any inner (let-bindings x))
 	      (any inner (let-body x)))]
-    ['app (either (p x)
+    ['app (or (p x)
 	      (any inner x))]
-    ['lambda (either (p x)
+    ['lambda (or (p x)
 		 (inner (lambda-body x)))]
-    ['if (either (p x) (any inner (cdr x)))]
+    ['if (or (p x) (any inner (cdr x)))]
+    ['case (or (p x)
+	       (any inner (map cadr (case-cases x)))
+	       (inner (case-switch x)))]
+    ['stack (or (p x) (inner (caddr x)))]
     [else (p x)]))
 
-(define (let-bindings e)
-  (define (pattern-match x body)
-    (if (eqv? (ast-type x) 'var)
-	(list (cons x body))
-	(let* ([constructor (car x)]
-	       [destructor (lambda (i) (dtor-name constructor i))])
-	  (flat-map (lambda (y i)
-		      (pattern-match y (list (destructor i) body)))
-		    (cdr x)
-		    (range 0 (length (cdr x)))))))
-  (flat-map (lambda (x) (pattern-match (car x) (cdr x))) (cadr e)))
+(define let-bindings cadr)
 (define let-body cddr)
 
+(define case-switch cadr)
+(define case-cases cddr)
+
+(define (constructor? data-layouts x)
+  (and (eqv? (ast-type x) 'var)
+       (assoc x (flat-map cdr data-layouts))))
+
+(define (all-cases data-layouts type)
+  (let ([sums (assoc type data-layouts)])
+    (if sums
+	(flat-map (lambda (sum)
+		    (let* ([sum-name (car sum)]
+			   [products (cdr sum)]
+			   [product-cases (map (lambda (y) (all-cases data-layouts y)) products)])
+		      (if (null? product-cases)
+			  (list sum-name) ; singletons aren't enclosed in a list [(foo x) 42] vs [foo 42]
+			  (apply combinations (cons (list sum-name) product-cases)))))
+		  (cdr sums))
+	'(:binding))))
+
+					; does a cover b
+(define (case-covers? data-layouts a b)
+  (let ([a-binding? (and (eqv? (ast-type a) 'var) (not (constructor? data-layouts a)))])
+    (cond
+     [(eqv? ':binding b) a-binding?]
+     [a-binding? #t]
+					; a literal/singleton
+     [(eqv? (ast-type b) 'var) (eqv? b a)]
+					; two different constructors
+     [(not (eqv? (car a) (car b))) #f]
+					; two same constructors
+     [else
+      (all (map (lambda (p q)
+		  (case-covers? data-layouts p q))
+		(cdr a) (cdr b)))])))
+
+(define (verify-cases data-layouts annotated-program)
+
+  ;; (define (check-pattern switch-type pat)
+
+  ;;   (define (impossible-match)
+  ;;     (error "Can't pattern match ~a with ~a" switch-type (ann-expr pat)))
+
+  ;;   (if (assoc switch-type data-layouts)
+  ;; 	(begin
+  ;; 	  (let ([sums (cdr (assoc switch-type data-layouts))])
+  ;; 	    (unless (eqv? (ast-type (ann-expr pat)) 'var) (impossible-match))
+  ;; 	    (unless (assoc (car (ann-expr pat)) sums) (impossible-match))
+  ;; 	    (unless 
+  ;; 	  )
+  ;;      (begin
+  ;; 	 (unless (assoc switch-type allowed-match-ast-types)
+  ;; 	   (error #f "Can't pattern match on ~a" switch-type))
+	 
+  ;; 	 (let ([allowed (cdr (assoc switch-type allowed-match-ast-types))])
+  ;; 	   (unless (assoc (ast-type (ann-expr pat)) allowed) (impossible-match)))))))
+
+  
+  (let ([expr (ann-expr annotated-program)])
+    (case (ast-type expr)
+      ['case
+	  (let* ([switch-type (ann-type (case-switch expr))]
+		 [cases (map car (case-cases expr))]
+		 [case-covered?
+		  (lambda (x) (any (lambda (y) (case-covers? data-layouts y x)) cases))])
+	    (unless (all (map case-covered? (all-cases data-layouts switch-type)))
+	      (error #f "not all cases covered")))]
+      [else (ast-traverse (lambda (x) (verify-cases data-layouts x)) expr)])))
+
+
+					; (let ([(foo a b) (foo 123 345)]) a)
+					;   |
+					;   v
+					; (let ([a (foo~0 (foo 123 345)]
+                                        ;       [b (foo~1 (foo 123 345)]) a)
+(define (expand-pattern-matches program)
+  (define (go x)
+    (define (let-pattern-match binding)
+      (let ([binding-name (car binding)]
+	    [body (cadr binding)])
+	(if (eqv? (ast-type binding-name) 'var)
+	    (list (list binding-name body))
+	    
+	    (let* ([sum-name (car binding-name)]
+		   [destructor (lambda (i) (dtor-name sum-name i))]
+		   [products (cdr binding-name)]
+
+		   [data-layouts (program-data-layouts program)]
+
+		   [type (data-tor-type data-layouts sum-name)]
+
+		   [sums (cdr (assoc type data-layouts))]
+		   [sum (assoc sum-name sums)]
+		   
+		   [expected-number (length (cdr sum))])
+
+					; assert that we only do a let pattern match on an ADT with exactly one sum
+	      (when (not (= 1 (length sums)))
+		(error #f (format "Cannot pattern match a ~a in a let since it has ~a possible constructors"
+				  type
+				  (length sums))))
+
+					; assert that there is the correct number of bindings
+	      (when (not (= (length products)
+			    expected-number))
+		(error #f (format "Got ~a bindings: expected ~a for ~a"
+			       (length products)
+			       expected-number
+			       binding)))
+	      
+	      (flat-map (lambda (y i)
+			  (let-pattern-match (list y `(,(destructor i) ,body))))
+			products
+			(range 0 (length products)))))))
+
+    (case (ast-type x)
+      ['let `(let ,(flat-map let-pattern-match (let-bindings x))
+	       ,@(map go (let-body x)))]
+      [else (ast-traverse go x)]))
+  (program-map-exprs go program))
+
 (define (lambda? x)
   (and (list? x) (eq? (car x) 'lambda)))
 
-
 (define (statement-type x)
   (cond
    [(and (list? x)
@@ -95,54 +214,78 @@
 	 (eqv? (car x) 'define)) 'define]
    [else 'expr]))
 
-(define (program-datas program)
-  (filter (lambda (x) (eqv? (statement-type x) 'data))
-	  program))
+
+					; (A ((foo (Int Bool))
+					;     (bar (Bool)))
+(define (program-data-layouts program)
+  (map (lambda (x) (cons (car x) (cdr x))) ; convert to assoc list
+       (map cdr (filter (lambda (x) (eqv? (statement-type x) 'data))
+			program))))
 
 (define (program-defines program)
   (filter (lambda (x) (eqv? (statement-type x) 'defines))
 	  program))
 
+(define (program-map-exprs f program)
+  (map (lambda (x)
+	 (case (statement-type x)
+	   ['expr (f x)]
+	   [else x]))
+       program))
+
 (define (program-body program)
+  ; hack to have multi-expression bodies
   `(let ()
      ,@(filter (lambda (x) (eqv? (statement-type x) 'expr))
 	       program)))
 
-					; gets both constructors and destructors
+(define (data-tor-type data-layouts tor)
+  (let* ([tors (flat-map data-tors data-layouts)]
+	 [info (cadr (assoc tor tors))])
+    (car info)))
+
+					; a data tor is either a constructor or destructor for an ADT
+					; data-tors returns constructors and destructors for a data-layout
 					; (data A (foo Int Bool)
 					;         (bar Bool))
 					;        |
 					;        v
-					; (foo . (abs Int (abs Bool A)))
-					; (foo~0 . (abs A Int)
-					; (foo~1 . (abs A Bool)
-					; (bar . (abs Bool A)
-					; (bar~0 . (abs A Bool)
+					; (foo   . ((A foo constructor) . (abs Int (abs Bool A))))
+					; (foo~0 . ((A foo 0 Int)       . (abs A Int)))
+					; (foo~1 . ((A foo 1 Bool)      . (abs A Bool)))
+					; (bar   . ((A bar constructor) . (abs Bool A)))
+					; (bar~0 . ((A bar 0 Bool)      . (abs A Bool)))
+					;  ------+-------------------------------------
+					;  tor   | info                 | type
 
-(define (data-tors data-def)
+(define (data-tors data-layout)
   (define (constructor-type t products)
     (fold-right (lambda (x acc) `(abs ,x ,acc)) t products))
 
   (define (destructor ctor-name prod-type part-type index)
-    (let ([name (dtor-name ctor-name index)])
-      (cons name `(abs ,prod-type ,part-type))))
+    (let* ([name (dtor-name ctor-name index)]
+	   [info (list prod-type ctor-name index part-type)])
+      (cons name (cons info `(abs ,prod-type ,part-type)))))
   
-  (let ([type-name (cadr data-def)]
-        [ctors (cddr data-def)])
+  (let ([type-name (car data-layout)]
+        [ctors (cdr data-layout)])
     (fold-right
      (lambda (ctor acc)       
        (let* ([ctor-name (car ctor)]
 	      [products (cdr ctor)]
 	      
-	      [maker (cons ctor-name (constructor-type type-name products))]
+	      [maker (cons ctor-name (cons (list type-name ctor-name 'constructor) (constructor-type type-name products)))]
 	      
 	      [dtors (map (lambda (t i) (destructor ctor-name type-name t i))
 			  products
 			  (range 0 (length products)))])
-	 
 	 (cons maker (append dtors acc))))
      '()
-     ctrs)))
+     ctors)))
+
+					; creates a type environment for a given adt definition
+(define (data-tors-type-env data-layout)
+  (map (lambda (x) (cons (car x) (cddr x))) (data-tors data-layout)))
 
 (define (dtor-name ctor-name index)
   (string->symbol
@@ -156,23 +299,109 @@
 (define lambda-args cadr)
 (define lambda-body caddr)
 
-					; utils
-(define (range s n)
-  (if (= 0 n) '()
-      (append (range s (- n 1))
-	      (list (+ s (- n 1))))))
+(define (references prog)
+  (ast-collect
+   (lambda (x)
+     (case (ast-type x)
+       ['var (list x)]
+       [else '()]))
+   prog))
+
+(define (graph bs)
+  (define (go bs orig-bs)
+    (if (null? bs)
+	'(() . ())
+	(let* [(bind (car bs))
+
+	       (vert (car bind))
+	       (refs (filter ; only count a reference if its a binding
+		      (lambda (x) (assoc x orig-bs))
+		      (references (cdr bind))))
+	       (edges (map (lambda (x) (cons vert x))
+			   refs))
+
+	       (rest (if (null? (cdr bs))
+			 (cons '() '())
+			 (go (cdr bs) orig-bs)))
+	       (total-verts (cons vert (car rest)))
+	       (total-edges (append edges (cdr rest)))]
+	  (cons total-verts total-edges))))
+  (go bs bs))
+
+(define (successors graph v)
+  (define (go v E)
+    (if (null? E)
+	'()
+	(if (eqv? v (caar E))
+	    (cons (cdar E) (go v (cdr E)))
+	    (go v (cdr E)))))
+  (go v (cdr graph)))
+
+					; takes in a graph (pair of vertices, edges)
+					; returns a list of strongly connected components
+
+					; ((x y w) . ((x . y) (x . w) (w . x))
+
+					; =>
+					; .->x->y
+					; |  |
+					; |  v
+					; .--w
+
+					; ((x w) (y))
+
+					; this uses tarjan's algorithm, to get reverse
+					; topological sorting for free
+(define (sccs graph)
+  
+  (let* ([indices (make-hash-table)]
+	 [lowlinks (make-hash-table)]
+	 [on-stack (make-hash-table)]
+	 [current 0]
+	 [stack '()]
+	 [result '()])
 
-(define (flat-map f . xs) (fold-left append '() (apply map (cons f xs))))
-(define (repeat x n) (if (<= n 0) '()
-			 (cons x (repeat x (- n 1)))))
+    (define (index v)
+      (get-hash-table indices v #f))
+    (define (lowlink v)
+      (get-hash-table lowlinks v #f))
 
+    (letrec
+	([strong-connect
+	  (lambda (v)
+	    (begin
+	      (put-hash-table! indices v current)
+	      (put-hash-table! lowlinks v current)
+	      (set! current (+ current 1))
+	      (push! stack v)
+	      (put-hash-table! on-stack v #t)
 
-(define-syntax push!
-  (syntax-rules ()
-    ((_ s x) (set! s (cons x s)))))
+	      (for-each
+	       (lambda (w)
+		 (if (not (hashtable-contains? indices w))
+					; successor w has not been visited, recurse
+		     (begin
+		       (strong-connect w)
+		       (put-hash-table! lowlinks
+					v
+					(min (lowlink v) (lowlink w))))
+					; successor w has been visited
+		     (when (get-hash-table on-stack w #f)
+		       (put-hash-table! lowlinks v (min (lowlink v) (index w))))))
+	       (successors graph v))
 
-(define-syntax pop!
-  (syntax-rules ()
-    ((_ s) (let ([x (car s)])
-	     (set! s (cdr s))
-	     x))))
+	      (when (= (index v) (lowlink v))
+		(let ([scc
+		       (let new-scc ()
+			 (let ([w (pop! stack)])
+			   (put-hash-table! on-stack w #f)
+			   (if (eqv? w v)
+			       (list w)
+			       (cons w (new-scc)))))])
+		  (set! result (cons scc result))))))])
+      (for-each
+       (lambda (v)
+	 (when (not (hashtable-contains? indices v)) ; v.index == -1
+	   (strong-connect v)))
+       (car graph)))
+    result))