尝试使用BNF

Question

我正在尝试使用BNF表示法。我在https://www.lua.org/manual/5.3/manual.html#9上看到了Lua5.3的完整语法。我想用{替换do和then，用}替换end：

stat ::=  ‘;’ | 
         varlist ‘=’ explist | 
         functioncall | 
         label | 
         break | 
         goto Name | 
         do block end |                                                  -> { block } 
         while exp do block end |                                        -> while exp { block }
         repeat block until exp |  
         if exp then block {elseif exp then block} [else block] end |    -> if exp { block .... } 
         for Name ‘=’ exp ‘,’ exp [‘,’ exp] do block end |               -> for ........  { block }  
         for namelist in explist do block end |                          -> for ........  { block }
         function funcname funcbody | 
         local function Name funcbody | 
         local namelist [‘=’ explist] 

funcbody ::= ‘(’ [parlist] ‘)’ block end                                  ->  ...........  { block }

如何使用上面修改过的语法来创建解释器？这能行得通吗？谢谢你的帮助。

Answer 1

将then替换为{，将end替换为}与表构造函数冲突：

if a then print(1) end

变成了

if a { print(1) }

相反，

a = {}

变成了

a = then end