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brag/brag/examples/lua-parser.rkt

111 lines
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Racket

#lang brag
;; Lua parser, adapted from:
;; http://www.lua.org/manual/5.1/manual.html#8
;;
chunk : (stat ["; "])* [laststat ["; "]]
block : chunk
stat : varlist "=" explist |
functioncall |
DO block END |
WHILE exp DO block END |
REPEAT block UNTIL exp |
IF exp THEN block (ELSEIF exp THEN block)* [ELSE block] END |
FOR NAME "=" exp "," exp ["," exp] DO block END |
FOR namelist IN explist DO block END |
FUNCTION funcname funcbody |
LOCAL FUNCTION NAME funcbody |
LOCAL namelist ["=" explist]
laststat : RETURN [explist] | BREAK
funcname : NAME ("." NAME)* [":" NAME]
varlist : var ("," var)*
var : NAME | prefixexp "[" exp "]" | prefixexp "." NAME
namelist : NAME ("," NAME)*
explist : (exp ",")* exp
;; 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 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.
;;
;; 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 ")"
functioncall : prefixexp args | prefixexp ":" NAME args
args : "(" [explist] ")" | tableconstructor | STRING
function : FUNCTION funcbody
funcbody : "(" [parlist] ")" block END
parlist : namelist ["," "..."] | "..."
tableconstructor : "{" [fieldlist] "}"
fieldlist : field (fieldsep field)* [fieldsep]
field : "[" exp "]" "=" exp | NAME "=" exp | exp
fieldsep : "," | ";"
binop : "+" | "-" | "*" | "/" | "^" | "%" | ".." |
"<" | "<=" | ">" | ">=" | "==" | "~=" |
AND | OR
unop : "-" | NOT | "#"