利用lex词法分析和yacc语法分析编写的简单编译器，主要完成实数和整型数据的加减乘除以及循环语句，条件语句，while语句，赋值语句等的处理-Use yacc lex lexical analysis and parsing write a simple compiler, mainly to complete the addition, subtraction and loops of real and integer data processing conditional statemen