LPeg语法奇怪

Question

我的Lua应用程序的一部分是一个搜索栏,我试图让它理解布尔表达式.我正在使用LPeg,但是当前的语法给出了一个奇怪的结果:

> re, yajl = require're', require'yajl'
> querypattern = re.compile[=[
    QUERY       <- ( EXPR / TERM )? S? !. -> {}
    EXPR        <- S? TERM ( (S OPERATOR)? S TERM )+ -> {}
    TERM        <- KEYWORD / ( "(" S? EXPR S? ")" ) -> {}
    KEYWORD     <- ( WORD {":"} )? ( WORD / STRING )
    WORD        <- {[A-Za-z][A-Za-z0-9]*}
    OPERATOR    <- {("AND" / "XOR" / "NOR" / "OR")}
    STRING      <- ('"' {[^"]*} '"' / "'" {[^']*} "'") -> {}
    S           <- %s+
]=]
> = yajl.to_string(lpeg.match(querypattern, "bar foo"))
"bar"
> = yajl.to_string(lpeg.match(querypattern, "name:bar AND foo"))
> = yajl.to_string(lpeg.match(querypattern, "name:bar AND foo"))
"name"
> = yajl.to_string(lpeg.match(querypattern, "name:'bar' AND foo"))
"name"
> = yajl.to_string(lpeg.match(querypattern, "bar AND (name:foo OR place:here)"))
"bar"

它只解析第一个令牌,我无法弄清楚它为什么会这样做.据我所知,部分匹配是不可能的,因为!.在起始非终端的末尾.我怎样才能解决这个问题？

Answer 1

匹配是获取整个字符串,但捕获是错误的.请注意,' - >'的优先级高于连接,因此您可能需要围绕这样的括号:

  EXPR        <- S? ( TERM ( (S OPERATOR)? S TERM )+ ) -> {}