diff --git a/beautiful-racket-demo/algebra-demo/main.rkt b/beautiful-racket-demo/algebra-demo/main.rkt
index 1b401d9..e8dd255 100644
--- a/beautiful-racket-demo/algebra-demo/main.rkt
+++ b/beautiful-racket-demo/algebra-demo/main.rkt
@@ -11,7 +11,7 @@
 (define tokenize-1
   (lexer
    [whitespace (token lexeme #:skip? #t)]
-   [(from/stop-before "%" "\n") (token 'COMMENT #:skip? #t)]
+   [(from/stop-before "#" "\n") (token 'COMMENT #:skip? #t)]
    [reserved-toks lexeme]
    [(:+ alphabetic) (token 'ID (string->symbol lexeme))]
    [(:+ (char-set "0123456789")) (token 'INT (string->number lexeme))]))
diff --git a/beautiful-racket-demo/algebra-demo/test.rkt b/beautiful-racket-demo/algebra-demo/test.rkt
index 4ac4204..5538708 100644
--- a/beautiful-racket-demo/algebra-demo/test.rkt
+++ b/beautiful-racket-demo/algebra-demo/test.rkt
@@ -1,6 +1,6 @@
 #lang algebra-demo
 fun f(x,y) = x + y
-% fun f(x,y) = x * y
+# fun f(x,y) = x * y
 fun g(zz) = f(zz,zz)
 g(10)
 g(23)
\ No newline at end of file
diff --git a/beautiful-racket-demo/precalc-demo/grammar.rkt b/beautiful-racket-demo/precalc-demo/grammar.rkt
index 5aee6bc..53b07e7 100644
--- a/beautiful-racket-demo/precalc-demo/grammar.rkt
+++ b/beautiful-racket-demo/precalc-demo/grammar.rkt
@@ -1,11 +1,11 @@
 #lang brag
 
-top : (func-def | func-app)*
-func-def : /"fun" var /"(" vars /")" /"=" expr
-/vars : [var (/"," var)*]
-@expr : sum
-sum : [sum ("+" | "-")] product
-product : [product ("*" | "/")] value
-@value : var | INT | func-app | /"(" expr /")"
-func-app : var /"(" [expr (/"," expr)*] /")"
+top : (fun | app)*
+fun : /"fun" var /"(" argvars /")" /"=" expr
+/argvars : [var (/"," var)*]
+@expr : s-or-d
+s-or-d : [s-or-d ("+" | "-")] p-or-q
+p-or-q : [p-or-q ("*" | "/")] value
+@value : var | INT | app | /"(" expr /")"
+app : var /"(" [expr (/"," expr)*] /")"
 @var : ID
\ No newline at end of file
diff --git a/beautiful-racket-demo/precalc-demo/main.rkt b/beautiful-racket-demo/precalc-demo/main.rkt
index 5c0308b..04b019b 100644
--- a/beautiful-racket-demo/precalc-demo/main.rkt
+++ b/beautiful-racket-demo/precalc-demo/main.rkt
@@ -1,6 +1,6 @@
 #lang br/quicklang
 (require brag/support "grammar.rkt")
-(provide (all-defined-out) #%module-begin)
+(provide top fun app s-or-d p-or-q)
 
 (module+ reader
   (provide read-syntax))
@@ -8,34 +8,36 @@
 (define-lex-abbrev reserved-toks
   (:or "fun" "(" ")" "=" "+" "*" "/" "-" ","))
 
-(define tokenize
-  (lexer
-   [(:or (from/to "//" "\n") (from/to "/*" "*/")) (token 'COMMENT #:skip? #t)]
-   [whitespace (tokenize input-port)]
+(define-lex-abbrev digits (char-set "0123456789"))
+
+(define tokenize-1
+  (lexer-srcloc
+   [whitespace (token lexeme #:skip? #t)]
+   [(:or (from/stop-before "#" "\n")
+         (from/to "/*" "*/")) (token 'COMMENT #:skip? #t)]
    [reserved-toks lexeme]
-   [alphabetic (token 'ID (string->symbol lexeme))]
-   [(:+ (char-set "0123456789")) (token 'INT (string->number lexeme))]))
+   [(:seq alphabetic (:* (:or alphabetic) digits)) (token 'ID (string->symbol lexeme))]
+   [(:seq (:? "-") (:+ digits)) (token 'INT (string->number lexeme))]))
 
-(define-macro top #'begin)
+(define-macro top #'#%module-begin)
 
-(define-macro (func-def VAR VARS EXPR)
-  #'(define (VAR . VARS) EXPR))
+(define-macro (fun VAR (ARGVAR ...) EXPR)
+  #'(define (VAR ARGVAR ...) EXPR))
 
-(define-macro-cases sum
+(define-macro-cases s-or-d
   [(_ LEFT "+" RIGHT) #'(+ LEFT RIGHT)]
   [(_ LEFT "-" RIGHT) #'(- LEFT RIGHT)]
   [(_ OTHER) #'OTHER])
 
-(define-macro-cases product
-  [(_ LEFT OP-STR RIGHT)
-   (with-syntax ([OP (string->symbol (syntax->datum #'OP-STR))])
-     #'(OP LEFT RIGHT))]
+(define-macro-cases p-or-q
+  [(_ LEFT "*" RIGHT) #'(* LEFT RIGHT)]
+  [(_ LEFT "/" RIGHT) #'(/ LEFT RIGHT)]
   [(_ OTHER) #'OTHER])
 
-(define-macro func-app #'#%app)
+(define-macro app #'#%app)
 
 (define (read-syntax src ip)
-  (define parse-tree (parse (λ () (tokenize ip))))
+  (define parse-tree (parse src (λ () (tokenize-1 ip))))
   (strip-context
    (with-syntax ([PT parse-tree])
      #'(module mod-name precalc-demo
diff --git a/beautiful-racket-demo/precalc-demo/test.rkt b/beautiful-racket-demo/precalc-demo/test.rkt
index be8bc72..9db0535 100644
--- a/beautiful-racket-demo/precalc-demo/test.rkt
+++ b/beautiful-racket-demo/precalc-demo/test.rkt
@@ -1,15 +1,15 @@
 #lang precalc-demo
 fun f(x, y, z) = x + x + x * (y + y) + y * z - z - z
 
-fun g(z) = f(z, z, z) // line comment
-g(10) // 300
+fun g42(z) = f(z, z, z) # line comment
+g42(-10) # = 300
 
-fun h() = g(10)
-h() // also 300
+fun h() = g42(10)
+h() # = 300
 
 fun k(x) = x / 10 / 10 / (x / x)
-k(h()) // 3
-k(10 * (15 + 3 * 5)) // 3
+k(h()) # = 3
+k(-10 * (15 + 3 * 5)) # = -3
 
 /*
 multiline comment