这是编译原理的源代码，涉及了编译原理的各个过程：词法分析，LL1语法分析，语义分析，中间代码生成，中间代码优化,中间代码生成目标代码，目标代码的解释执行-This is the principle of compiling source code, the various principles involved in the compilation process: lexical analysis, LL1 parsing, semantic analysis, intermediate co