电子科技大学编译技术icoding--实验一 词法分析

请根据词法分析实验中给定的文法，利用flex设计一词法分析器，该分析器从标准输入读入源代码后，输出单词的类别编号及附加信息。 附加信息规定如下： 当类别为 Y_ID、num_INT 或 num_FLOAT 时，附加信息为该类别对应的属性，如 main, 100, 29.3等； 当类别为 关键字 时，附件信息为 KEYWORD； 当类别为 运算符 时，附件信息为 OPERATOR； 当类别为 其它符号时，附件信息为 SYMBOL； 例如对于源代码

int main(){
    return 3;
}

词法分析器的输出为：

<261, KEYWORD>
<260, main>
<285, SYMBOL>
<286, SYMBOL>
<287, SYMBOL>
<269, KEYWORD>
<258, 3>
<292, SYMBOL>
<288, SYMBOL>

请在本页面上传词法分析实验所有源代码及实验报告（源代码至少包括一个flex源文件，即 .l 文件，如有其它 .c 或 .h 文件，也请一并上传）

本实验中的单词类别定义如下，该定义包含在 token.h 中，此头文件可直接使用，无需上传

// 单词类别
enum yytokentype {
	num_INT = 258,
	num_FLOAT = 259,

	Y_ID = 260,

	Y_INT = 261,
	Y_VOID = 262,
	Y_CONST = 263,
	Y_IF = 264,
	Y_ELSE = 265,
	Y_WHILE = 266,
	Y_BREAK = 267,
	Y_CONTINUE = 268,
	Y_RETURN = 269,

	Y_ADD = 270,
	Y_SUB = 271,
	Y_MUL = 272,
	Y_DIV = 273,
	Y_MODULO = 274,
	Y_LESS = 275,
	Y_LESSEQ = 276,
	Y_GREAT = 277,
	Y_GREATEQ = 278,
	Y_NOTEQ = 279,
	Y_EQ = 280,
	Y_NOT = 281,
	Y_AND = 282,
	Y_OR = 283,
	Y_ASSIGN = 284,

	Y_LPAR = 285,
	Y_RPAR = 286,
	Y_LBRACKET = 287,
	Y_RBRACKET = 288,
	Y_LSQUARE = 289,
	Y_RSQUARE = 290,
	Y_COMMA = 291,
	Y_SEMICOLON = 292,

	Y_FLOAT = 293
};

 

%{
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char* endptr;
enum yytokentype {
	num_INT = 258,
	num_FLOAT = 259,

	Y_ID = 260,

	Y_INT = 261,
	Y_VOID = 262,
	Y_CONST = 263,
	Y_IF = 264,
	Y_ELSE = 265,
	Y_WHILE = 266,
	Y_BREAK = 267,
	Y_CONTINUE = 268,
	Y_RETURN = 269,

	Y_ADD = 270,
	Y_SUB = 271,
	Y_MUL = 272,
	Y_DIV = 273,
	Y_MODULO = 274,
	Y_LESS = 275,
	Y_LESSEQ = 276,
	Y_GREAT = 277,
	Y_GREATEQ = 278,
	Y_NOTEQ = 279,
	Y_EQ = 280,
	Y_NOT = 281,
	Y_AND = 282,
	Y_OR = 283,
	Y_ASSIGN = 284,

	Y_LPAR = 285,
	Y_RPAR = 286,
	Y_LBRACKET = 287,
	Y_RBRACKET = 288,
	Y_LSQUARE = 289,
	Y_RSQUARE = 290,
	Y_COMMA = 291,
	Y_SEMICOLON = 292,

	Y_FLOAT = 293
};
int a1;
float a2;
%}

DIGIT [0-9]+
WORD  [a-zA-Z]+
DIGIT16 [0-9a-fA-F]+

%%
0[xX]{DIGIT16}   {a1 = strtol(yytext, &endptr, 16); return num_INT;}
[0-9]+       {a1 = atoi(yytext); return num_INT;}
{DIGIT}+"."*{DIGIT}*      {a2 = atoi(yytext); return num_FLOAT;}

"//"(.*)   {yywrap();}
"\n"        {}
" "         {}
"int"       {return Y_INT;}
"void"      {return Y_VOID;}
"const"     {return Y_CONST;}
"if"        {return Y_IF;}
"else"      {return Y_ELSE;}
"while"     {return Y_WHILE;}
"break"     {return Y_BREAK;}
"continue"  {return Y_CONTINUE;}
"return"    {return Y_RETURN;}

[a-zA-Z_][a-zA-Z0-9_]*    {return Y_ID;}

"+"         {return Y_ADD; }
"-"         {return Y_SUB; }
"*"         {return Y_MUL; }
"/"         {return Y_DIV; }
"%"         {return Y_MODULO; }
"<"         {return Y_LESS; }
"<="        {return Y_LESSEQ; }
">"         {return Y_GREAT; }
">="        {return Y_GREATEQ; }
"!="        {return Y_NOTEQ;}
"=="        {return Y_EQ; }
"!"         {return Y_NOT;}
"&&"        {return Y_AND;}
"||"        {return Y_OR;}
"="         {return Y_ASSIGN;}

"("         {return Y_LPAR;}
")"         {return Y_RPAR; }
"{"         {return Y_LBRACKET;}
"}"         {return Y_RBRACKET;}
"["         {return Y_LSQUARE;}
"]"         {return Y_RSQUARE;}
","         {return Y_COMMA;}
";"         {return Y_SEMICOLON;}

"."         {return Y_FLOAT;}
%%

void main()
{
	int tok;
	
	while(tok = yylex()) 
	{	
		if(tok == Y_ID)
				printf("<260, %s>\n", yytext);
			else if(tok == num_INT)
				printf("<258, %d>\n", a1);
			else if(tok == num_FLOAT)
				printf("<259, %f>\n", a2);
			else if(tok == Y_INT || tok == Y_VOID || tok == Y_CONST || tok == Y_IF || tok == Y_ELSE || tok == Y_WHILE || tok == Y_BREAK ||  tok == Y_CONTINUE ||  tok == Y_RETURN)
				printf("<%d, %s>\n", tok, "KEYWORD");
			else if(tok == Y_ADD || tok == Y_SUB || tok == Y_MUL || tok == Y_DIV || tok == Y_MODULO || tok == Y_LESS || tok == Y_LESSEQ ||  tok == Y_GREAT ||  tok == Y_GREATEQ || tok == Y_NOTEQ || tok == Y_EQ || tok == Y_NOT || tok == Y_AND || tok == Y_OR || tok == Y_ASSIGN)
				printf("<%d, %s>\n", tok, "OPERATOR");
			else if(tok == Y_LPAR || tok == Y_RPAR || tok == Y_LBRACKET || tok == Y_RBRACKET || tok == Y_LSQUARE || tok == Y_RSQUARE || tok == Y_COMMA ||  tok == Y_SEMICOLON || tok == Y_FLOAT)
				printf("<%d, %s>\n", tok, "SYMBOL");
	}
}

int yywrap(){	
    return 1;  
    }

本实验应用flex，实验前建议在本地安装好flex，可通过cmd命令直接操作。

flex test.l

编译lex.yy.c文件时，个人应用cmd命令调用gcc编译，较为方便。

gcc lex.yy.c

上传文件时，请将实验报告（Word文档或PDF文档）一并上传，否则系统不予通过。

实验要点：        单行注释的正则表达式及忽略处理

                          变量名的正则表达式

                          十六进制数如何转化为十进制数

                          flex自身全局变量和已定义函数的合理调用

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