按一定规则读取文件内容，并输出；这是把flex文件转换成C编码，可在C/C++文件中直接调用-Read the contents of the file according to certain rules, and outputs This is the flex file into C code can be C/C++ files directly call

基于flex和bison的终端计算器代码，如果想要初步编译产生的.c代码能在VC环境下编译的话，请在.l文件的开始加上 option yywrap-Terminal based on flex and bison calculator code, if you want to produce a preliminary compilation. C code in VC environment compiler, please. L beginning of the file plus opt