Parsing.

05-parsing/main.rkt

@@ -1,8 +1,45 @@
-;; The first three lines of this file were inserted by DrRacket. They record metadata
+#lang pl
-;; about the language level of this file in a form that our tools can easily process.
-#reader(lib "htdp-intermediate-reader.ss" "lang")((modname main) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
-#|
 
+(define-type AE
+  [R1 Prod AE]
+  [R2 Prod])
+
+(define-type Prod
+  [R3 Atom Prod]
+  [R4 Atom])
+
+(define-type Atom
+  [R5 Number]
+  [R6 AE])
+
+; Symbols:
+; 'sum
+; 'mul
+; 'groups
+; 'groupe
+
+; parse-ae: s: Sexpr → AE
+(: parse-ae : (Sexpr -> AE))
+; Parse a Sexpr.
+(define (parse-ae s)
+  ; parseae: s: Sexpr, a: Sexpr → AE
+  (: parseae : (Sexpr Sexpr -> AE))
+  ; Parse a Sexpr and while accumulating in a.
+  (define (parseae s a)
+    (match s
+      [(list prod ae) (parseae/group (rest s) '())]
+      [(cons (number: n) r) (R2 (R4 (R5 n)))]))
+
+  (parseae s '()))
+
+
+(test (parse-ae '(3)) => (R2 (R4 (R5 3))))
+(test (parse-ae '(groups 3 groupe)) => (R2 (R4 (R6 (R2 (R4 (R5 3)))))))
+(test (parse-ae '(1 plus 1)) => (R1 (R4 (R5 1)) (R2 (R4 (R5 1)))))
+
+; parse-ae/h: s: Sexpr, ae: AE → AE
+
+#|
 <AE> ::= <PROD> + <AE> (1)
          | <PROD> (2)