encoding the operator precedence rules as part of the grammar. It wou…

…ld make a great test case, when ragg supports precedence, to make sure we get the same results.

ragg/examples/lua-parser.rkt

@@ -32,28 +32,57 @@ var :  NAME | prefixexp "[" exp "]" | prefixexp "." NAME
 namelist : NAME ("," NAME)*
 
 explist : (exp ",")* exp
-
-;; FIXME: handle exp operator precedences.
+
+
+;; Note by dyoo: The parsing of exp deviates from Lua in that we have these administrative
+;; rules to explicitly represent the precedence rules.
+;;              
 ;; See: http://www.lua.org/manual/5.1/manual.html#2.5.6
 ;;
-;;
+;; Ragg doesn't yet automatically desugar operator precedence rules.
+;; I'm doing it by hand at the moment, which is not ideal, so a future version of
+;; ragg will have a story about describing precedence.
+;;              
 ;; Operator precedence in Lua follows the table below, from lower to higher priority:
 ;;
-;;     or
-;;     and
-;;     <     >     <=    >=    ~=    ==
-;;     ..
-;;     +     -
-;;     *     /     %
-;;     not   #     - (unary)
-;;     ^              
+;;     or                                                 exp_1
+;;     and                                                exp_2 
+;;     <     >     <=    >=    ~=    ==                   exp_3
+;;     ..                                                 exp_4
+;;     +     -                                            exp_5
+;;     *     /     %                                      exp_6
+;;     not   #     - (unary)                              exp_7
+;;     ^                                                  exp_8
 ;;
 ;; As usual, you can use parentheses to change the precedences of an expression.
 ;; The concatenation ('..') and exponentiation ('^') operators are right associative.
 ;; All other binary operators are left associative.
-
-exp :  NIL | FALSE | TRUE | NUMBER | STRING | "..." | function | 
-         prefixexp | tableconstructor | exp binop exp | unop exp 
+;;
+;; The original grammar rule before encoding precedence was:
+;;
+;; exp :  NIL | FALSE | TRUE | NUMBER | STRING | "..." | function | 
+;;         prefixexp | tableconstructor | exp binop exp | unop exp 
+
+exp :  exp_1
+exp_1: exp_1 binop_1 exp_2 | exp_2
+exp_2: exp_2 binop_2 exp_3 | exp_3
+exp_3: exp_3 binop_3 exp_4 | exp_4
+exp_4: exp_5 binop_4 exp_4 | exp_5           ;; right associative
+exp_5: exp_5 binop_5 exp_6 | exp_6
+exp_6: exp_6 binop_6 exp_7 | exp_7
+exp_7: unop exp_8
+exp_8: exp_9 binop_8 exp_8 | exp_9           ;; right associative
+exp_9: NIL | FALSE | TRUE | NUMBER | STRING | "..." | function | 
+         prefixexp | tableconstructor 
+binop_1: OR
+binop_2: AND
+binop_3: "<" | ">" | "<=" | ">=" | "~=" | "=="
+binop_4: ".."
+binop_5: "+" | "-"
+binop_6: "*" | "/" | "%"
+binop_8: "^"               
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
 
 prefixexp : var | functioncall | "(" exp ")"