tidier

beautiful-racket-demo/basic-demo-2/expr.rkt

@@ -1,29 +1,28 @@
 #lang br
-(provide (all-defined-out))
+(provide b-expr b-sum b-product b-neg b-expt)
+
+(define (b-expr expr)
+  (if (integer? expr) (inexact->exact expr) expr))
 
-;; b-sum : b-product (("+" | "-")  b-product)*
 (define-macro-cases b-sum
-  [(_ PROD) #'PROD]
-  [(_ LEFT-PROD "+" RIGHT-PROD) #'(+ LEFT-PROD RIGHT-PROD)]
-  [(_ LEFT-PROD "-" RIGHT-PROD) #'(- LEFT-PROD RIGHT-PROD)])
+  [(_ VAL) #'VAL]
+  [(_ LEFT "+" RIGHT) #'(+ LEFT RIGHT)]
+  [(_ LEFT "-" RIGHT) #'(- LEFT RIGHT)])
 
-;; b-product : [b-product ("*"|"/"|"%"|"^")] b-value
 (define-macro-cases b-product
   [(_ VAL) #'VAL]
   [(_ LEFT "*" RIGHT) #'(* LEFT RIGHT)]
   [(_ LEFT "/" RIGHT) #'(/ LEFT RIGHT 1.0)]
   [(_ LEFT "mod" RIGHT) #'(modulo LEFT RIGHT)])
 
-;; b-expt : [b-expt "^"] b-value
+(define-macro-cases b-neg
+  [(_ VAL) #'VAL]
+  [(_ "-" VAL) #'(- VAL)])
+
 (define-macro-cases b-expt
   [(_ VAL) #'VAL]
   [(_ LEFT "^" RIGHT) #'(expt LEFT RIGHT)])
 
-(define (b-expr expr)
-  (if (integer? expr) (inexact->exact expr) expr))
-
-(define (b-negative num) (- num))
-
 (define (b-not expr) (if (zero? expr) 1 0))
 
 (define-macro (b-def ID VAR EXPR)

beautiful-racket-demo/basic-demo-2/lexer.rkt

@@ -3,7 +3,7 @@
 
 (define-lex-abbrev digits (:+ (char-set "0123456789")))
 
-(define-lex-abbrev reserved-terms (:or "print" "goto" "end" "+" ":" "let" "=" "gosub" "return" "-" "for" "to" "step" "next" "if" "then" "else" "and" "or" "<" ">" "*" "/" "(" ")" "^" "!" "mod" "input" ";" "def"))
+(define-lex-abbrev reserved-terms (:or "print" "goto" "end" "+" ":" ";" "let" "=" "input" "-" "*" "/" "^" "mod" "(" ")" "def" "if" "then" "else" "and" "or" "<" ">" "!" "gosub" "return" "for" "to" "step" "next"))
 
 (define basic-lexer
   (lexer-srcloc

beautiful-racket-demo/basic-demo-2/parser.rkt

@@ -16,23 +16,20 @@ b-if : /"if" b-expr /"then" b-expr [/"else" b-expr]
 b-gosub : /"gosub" b-expr
 b-return : /"return"
 b-input : /"input" b-id
+@b-id : ID
 b-def :  /"def" b-id /"(" b-id /")" /"=" b-expr
 b-for : /"for" b-id /"=" b-expr /"to" b-expr [/"step" b-expr]
 b-next : /"next" [b-id]
 
-;; expressions with precedence & order
 b-expr : b-logic-expr 
 b-logic-expr : [b-logic-expr ("and" | "or")] b-comp-expr
 b-comp-expr : [b-comp-expr ("=" | "<" | ">")] b-sum
 b-sum : [b-sum ("+"|"-")] b-product
-b-product : [b-product ("*"|"/"|"mod")] b-expt
-b-expt : [b-expt "^"] b-value
+b-product : [b-product ("*"|"/"|"mod")] b-neg
+b-neg : ["-"] b-expt
+b-expt : [b-expt ("^")] b-value
 
-;; values
-@b-value : b-id | b-number | /"(" b-expr /")" | b-not | b-func
+@b-value : b-number | b-id | /"(" b-expr /")" | b-not | b-func
 /b-func : b-id /"(" b-expr /")"
 b-not : /"!" b-value
-@b-id : ID
-@b-number : b-positive | b-negative
-@b-positive : INTEGER | DECIMAL
-b-negative : /"-" b-positive
+@b-number : INTEGER | DECIMAL