句型分析，语法分析

 

Parsing is the process of determing if a string of token can be generated by a grammar.

Most parsing methods fall into one of two classes,called the top-down and bottom-up methods.

These terms refer to the order in which nodes in the parse tree are constructed.In the former,construction starts at the root and proceeds towards the leaves,while,in the later,construction starts at the leaves and proceeds towards the root.