编译原理实验报告词法分析器制作与应用设计思想(1)程序主体结构部分：说明部分%%规则部分%%辅助程序部分（2）主体结构的说明在这里说明部分告诉我们使用的LETTER,DIGIT, IDENT(标识符,通常定义为字母开头的字母数字串)和STR(字符串常量,通常定义为双引号括起来的一串字符)是什么意思.这部分也可以包含一些初始化代码.例如用#include来使用标准的头文件和前向说明(forward ，references).这些代码应该再标记"%{"和"%}"之间;规则部分>可以包括任何你想用来分析的代码;我们这里包括了忽略所有注释中字符的功能,传送ID名称和字符串常量内容到主调函数和main函数的功能.（3）实现原理程序中先判断这个句语句中每个单元为关键字、常数、运算符、界符，对与不同的单词符号给出不同编码形式的编码，用以区分之。

PL/0语言的EBNF表示<常量定义>：：=<标识符>=<无符号整数>;<标识符>：：=<字母>={<字母>|<数字>};<加法运算符>::=+|-<乘法运算符>::=*|/<关系运算符>::==|#|<|<=|>|>=<字母>::=a|b|…|X|Y|Z<数字>::=0|1|2|…|8|9三：设计过程1．关键字：void，main，if，then，break，int，Char，float，include，for，while，printfscanf 并为小写。

2．"+”;”-”;”*”;”/”;”:=“;”:”;”<“;”<=“;”>“;”>=“;”<>“;”=“;”(“;”)”;”;”;”#”为运算符。

3．其他标记如字符串，表示以字母开头的标识符。

4．空格符跳过。

5．各符号对应种别码关键字分别对应1-13运算符分别对应401-418，501-513。

字符串对应100常量对应200结束符#四：举例说明目标：实现对常量的判别代码：digit [0-9]letter [A-Za-z]other_char [!-@\[-~]id ({letter}|[_])({letter}|{digit}|[_])*string {({letter}|{digit}|{other_char})+}int_num {digit}+%%[ |\t|\n]+ "auto"|"double"|"int"|"struct"|"break"|"else"|"long"|"switch"|"case"|"enum"|"register"|"typedef"|"ch ar"|"extern"|"return"|"union"|"const"|"float"|"short"|"unsigned"|"continue"|"for"|"signed"|"void"|"d efault"|"goto"|"sizeof"|"do"|"if"|"static"|"while"|"main"{Upper(yytext,yyleng);printf("%s,NULL\n",yytext);}\"([!-~])*\" {printf("CONST_string,%s\n",yytext);}-?{int_num}[.]{int_num}?([E][+|-]?{int_num})? {printf("CONST_real,%s\n",yytext);} "0x"?{int_num} {printf("CONST_int,%s\n",yytext);} ","|";"|"("|")"|"{"|"}"|"["|"]"|"->"|"."|"!"|"~"|"++"|"--"|"*"|"&"|"sizeof"|"/"|"%"|"+"|"-"|">"|"<"|">="|" <="|"=="|"!="|"&"|"^"|"|"|"&"|"||"|"+="|"-="|"*="|"/="|"%="|">>="|"<<="|"&="|"^="|"|="|"=" {printf("%s,NULL\n",yytext);}{id} {printf("ID,%s\n",yytext);}{digit}({letter})+ {printf("error1:%s\n",yytext);}%%#include <ctype.h>Upper(char *s,int l){int i;for(i=0;i<l;i++){s[i]=toupper(s[i]);}}yywrap(){return 1;}五：DFA六:数据测试七：心得体会其实匹配并不困难，主要是C++知识要求相对较高，只要把握住指针就好了。

附源程序：#include<iostream.h>#include<stdio.h>#include<stdlib.h>#include<string.h>int i,j,k,flag,number,status;/*status which is use to judge the string is keywords or not!*/char ch;char words[10] = {" "};char program[500];int Scan(char program[]){char *keywords[13] = {"void","main","if","then","break","int", "char","float","include","for","while","printf","scanf"};number = 0;status = 0;j = 0;ch = program[i++];/* To handle the lettle space ands tab*//*handle letters*/if ((ch >= 'a') && (ch <= 'z' )){while ((ch >= 'a') && (ch <= 'z' )){words[j++]=ch;ch=program[i++];}i--;words[j++] = '\0';for (k = 0; k < 13; k++)if (strcmp (words,keywords[k]) == 0)switch(k){case 0:{flag = 1;status = 1;break;}case 1:{flag = 2;status = 1;break;}case 2:{ flag = 3; status = 1; break;}case 3:{ flag = 4; status = 1; break;}case 4:{ flag = 5; status = 1; break;}case 5:{ flag = 6; status = 1; break;} case 6:{ flag = 7; status = 1; break;} case 7:{ flag = 8; status = 1; break;} case 8:{ flag = 9; status = 1; break;} case 9:{ flag = 10; status = 1; break;} case 10:{ flag = 11; status = 1; break;}case 11:{flag = 12;status = 1;break;}case 12:{flag = 13;status = 1;break;}}if (status == 0){flag = 100;}}/*handle digits*/else if ((ch >= '0') && (ch <= '9')) {number = 0;while ((ch >= '0' ) && (ch <= '9' )) {number = number*10+(ch-'0');ch = program[i++];}flag = 200;i--;}/*opereation and edge handle*/ else switch (ch){case '=':{if (ch == '=')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 401;}else{i--;flag = 402;}break;}case'>':{if (ch == '>')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 403;}else{i--;flag = 404;}break;}case'<':{if (ch == '<')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 405;}else{i--;flag = 406;}break;}case'!':{if (ch == '!')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 407;}else{i--;flag = 408;}break;}case'+':{if (ch == '+')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 409;}else if (ch == '+'){words[j++] = ch;words[j] = '\0';flag = 410;}else{i--;flag = 411;}break;}case'-':{if (ch == '-')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 412;}else if( ch == '-'){words[j++] = ch;words[j] = '\0';flag = 413;}else{i--;flag = 414;}break;}case'*':{if (ch == '*')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 415;}else{i--;flag = 416;}break;}case'/':{if (ch == '/')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 417;}else{i--;flag = 418;}break;}case';':{words[j] = ch; words[j+1] = '\0';flag = 501; break;}case'(':{words[j] = ch; words[j+1] = '\0';flag = 502; break;}case')':{words[j] = ch; words[j+1] = '\0';flag = 503; break;}case'[':{words[j] = ch; words[j+1] = '\0';flag = 504; break;}case']':{words[j] = ch; words[j+1] = '\0';flag = 505; break;}case'{':{words[j] = ch;words[j+1] = '\0';flag = 506;break;}case'}':{words[j] = ch;words[j+1] = '\0';flag = 507;break;}case':':{words[j] = ch;words[j+1] = '\0';flag = 508;break;}case'"':{words[j] = ch;words[j+1] = '\0';flag = 509;break;}case'%':{if (ch == '%')words[j++] = ch;words[j] = '\0';ch = program[i++];if (ch == '='){words[j++] = ch;words[j] = '\0';flag = 510;}else{i--;flag = 511;}break;}case',':{words[j] = ch;words[j+1] = '\0';flag = 512;break;}case'#':{words[j] = ch;words[j+1] = '\0';flag = 513;break;}case'@':{words[j] = '#';flag = 0;break;}default:{flag = -1;break;}}return flag;}main(){i=0;printf("please input a program end with @"); do{ch = getchar();program[i++] = ch;}while(ch != '@');i = 0;do{flag = Scan(program);if (flag == 200){printf("(%2d,%4d)",flag,number);}else if (flag == -1){printf("(%d,error)",flag);}else{printf("(%2d,%4s)",flag,words);}}while (flag != 0);system("pause");}编译原理》实验教学大纲部门:实验中心发布人:崔诣时间:2006-7-4课程编号：27140001 大纲执笔人：马知行课程名称：编译原理大纲审批人：曹启君英文名称：Compilers Principles课程学时：54 实验学时：36实验室名称：计算机技术实验室实验课性质：非独立设课适用专业：计算机科学与技术一、本课程实验教学目的与要求通过对词法分析、语法分析和代码生成程序的设计和编制，使学生掌握编译程序的基本构造、基本原理和主要实现技巧。