递归子程序法：对应每个非终结符语法单元编一个独立的处理过程（或子程序）。语法分析从读入第一个单词开始，由非终结符<程序>（即开始符）出发，沿语法描述图箭头所指出的方向进行分析。当-Recursive Subroutine law: at the end of the corresponding syntax for each non-unit provision of an independent process (or subprogram). Parsing from the first words read in the beginning, by a non-terminator <program> (that is, at the beginning), the syntax descr iption diagram along the arrows pointed out the direction for analysis. When