Initial Neerdowell notes and code cleanup.

Author: dvanhorn

langs/neerdowell/ast.rkt

@@ -7,9 +7,6 @@
 ;; type Defn = (Defn Id (Listof Id) Expr)
 (struct Defn (f xs e) #:prefab)
 
-;; type StructDefn = (Struct Id (Listof Id))
-(struct Struct (name flds) #:prefab)
-
 ;; type Expr  = (Eof)
 ;;            | (Quote Datum)
 ;;            | (Prim Op (Listof Expr))

langs/neerdowell/compile-ops.rkt

@@ -324,12 +324,17 @@
           (Add rax r8)
           (Mov rax (Offset rax 0)))]))
 
+;; Nat -> Asm
+;; Emit instructions for creating a structure of length n
+;; using values on top of stack
 (define (compile-make-struct n)
   (seq (compile-make-struct/a n 1)
        (Mov rax rbx)
        (Or rax type-struct)
        (Add rbx (* 8 n))))
 
+;; Nat Nat -> Asm
+;; Pop elements off stack, writing them to heap
 (define (compile-make-struct/a n i)
   (if (= n i)
       (seq (Mov (Offset rbx (* 8 (- n i))) rax))

langs/neerdowell/interp-prims.rkt

@@ -2,8 +2,10 @@
 (require "ast.rkt")
 (provide interp-prim)
 
+;; type Struct = (StructVal Symbol (Vectorof Value))
 (struct StructVal (name vals))
 
+;; Op [Listof Value] -> Answer
 (define (interp-prim p vs)
   (match (cons p vs)
     ;; Op0
@@ -58,7 +60,7 @@
      (if (<= 0 v2 (sub1 (string-length v1)))
          (string-ref v1 v2)
          'err)]
-    [(list 'struct? (? symbol? s) v)
+    [(list 'struct? s v)
      (match v
        [(StructVal n _) (eq? s n)]
        [_ #f])]
@@ -67,7 +69,7 @@
      (if (<= 0 v2 (sub1 (vector-length v1)))
          (vector-set! v1 v2 v3)
          'err)]
-    [(list 'struct-ref (? symbol? s) (? integer? i) (StructVal n vs))
+    [(list 'struct-ref s i (StructVal n vs))
      (if (and (eq? s n) (<= 0 i (sub1 (vector-length vs))))
          (vector-ref vs i)
          'err)]

langs/neerdowell/parse.rkt

@@ -1,28 +1,31 @@
 #lang racket
-(provide parse parse-define parse-e)
+(provide parse parse-define parse-e parse-struct)
 (require "ast.rkt")
 
 ;; [Listof S-Expr] -> Prog
 (define (parse s)
   (match s
     [(cons (and (cons 'struct _) d) s)
      (match (parse s)
-       [(Prog ds e)       
-        (Prog (append (make-struct-defns (parse-struct d)) ds) e)])]
+       [(Prog ds e)
+        (Prog (append (parse-struct d) ds) e)])]
     [(cons (and (cons 'define _) d) s)
      (match (parse s)
        [(Prog ds e)
         (Prog (cons (parse-define d) ds) e)])]
     [(cons e '()) (Prog '() (parse-e e))]
     [_ (error "program parse error")]))
 
-;; Struct -> [Listof Defn]
-(define (make-struct-defns s)
+;; S-Expr -> [Listof Defn]
+(define (parse-struct s)
   (match s
-    [(Struct n flds)
-     (list* (make-struct-defn-construct n flds)
-            (make-struct-defn-predicate n)
-            (make-struct-defn-accessors n (reverse flds)))]))
+    [(list 'struct (? symbol? n) flds)
+     (if (andmap symbol? flds)
+         (list* (make-struct-defn-construct n flds)
+                (make-struct-defn-predicate n)
+                (make-struct-defn-accessors n (reverse flds)))
+         (error "parse struct definition error"))]
+    [_ (error "parse struct definition error")]))
 
 ;; Id [Listof Id] -> [Listof Defn]
 (define (make-struct-defn-construct n flds)
@@ -33,28 +36,23 @@
 (define (make-struct-defn-predicate n)
   (Defn (symbol-append n '?) (list 'x)
     (Prim 'struct? (list (Quote n) (Var 'x)))))
-     
+
 ;; Id [Listof Id] -> [Listof Defn]
 (define (make-struct-defn-accessors n flds)
   (match flds
     ['() '()]
     [(cons f flds)
      (cons (Defn (symbol-append n '- f) (list 'x)
-             (Prim 'struct-ref (list (Quote n) (Quote (length flds)) (Var 'x))))
+             (Prim 'struct-ref
+                   (list (Quote n)
+                         (Quote (length flds))
+                         (Var 'x))))
            (make-struct-defn-accessors n flds))]))
 
 ;; Symbol ... -> Symbol
 (define (symbol-append . ss)
-  (string->symbol (apply string-append  (map symbol->string ss))))
-
-;; S-Expr -> StructDefn
-(define (parse-struct s)
-  (match s
-    [(list 'struct (? symbol? n) flds)
-     (if (andmap symbol? flds)
-         (Struct n flds)
-         (error "parse struct definition error"))]
-    [_ (error "parse struct definition error")]))
+  (string->symbol
+   (apply string-append (map symbol->string ss))))
 
 ;; S-Expr -> Defn
 (define (parse-define s)
@@ -76,7 +74,7 @@
     [(list (? (op? op1) p1) e)     (Prim p1 (list (parse-e e)))]
     [(list (? (op? op2) p2) e1 e2) (Prim p2 (list (parse-e e1) (parse-e e2)))]
     [(list (? (op? op3) p3) e1 e2 e3)
-     (Prim p3 (list (parse-e e1) (parse-e e2) (parse-e e3)))]    
+     (Prim p3 (list (parse-e e1) (parse-e e2) (parse-e e3)))]
     [(list 'begin e1 e2)
      (Begin (parse-e e1) (parse-e e2))]
     [(list 'if e1 e2 e3)
@@ -91,7 +89,7 @@
          (Lam (gensym 'lambda) xs (parse-e e))
          (error "parse lambda error"))]
     [(cons e es)
-     (App (parse-e e) (map parse-e es))]    
+     (App (parse-e e) (map parse-e es))]
     [_ (error "Parse error" s)]))
 
 (define (parse-match e ms)

www/notes.scrbl

@@ -32,4 +32,5 @@ suggestions for improving the material, @bold{please},
 @include-section{notes/loot.scrbl}
 @include-section{notes/mug.scrbl}
 @include-section{notes/mountebank.scrbl}
+@include-section{notes/neerdowell.scrbl}
 @;include-section{notes/shakedown.scrbl}