Left-to-right and Leftmost derivation Parsing (LL Parsing)
LL 分析（Left-to-right and Leftmost derivation Parsing） 是处理 上下文无关语法 的 自顶向下分析 算法，它从左往右扫描输入，并对句型执行 最左推导 得到语法树。
能够被 LL 分析 的 形式语法 被称为 LL 文法。
使用
其中，LL(k+1) 语言包含 LL(k) 语言（k>=0)：
In computer science, an LL parser (Left-to-right, leftmost derivation) is a top-down parser for a restricted context-free language. It parses the input from Left to right, performing Leftmost derivation of the sentence.
An LL parser is called an LL(k) parser if it uses k tokens of lookahead when parsing a sentence. A grammar is called an LL(k) grammar if an LL(k) parser can be constructed from it. A formal language is called an LL(k) language if it has an LL(k) grammar. The set of LL(k) languages is properly contained in that of LL(k+1) languages, for each k ≥ 0.[1] A corollary of this is that not all context-free languages can be recognized by an LL(k) parser.[1]