// Lexical_Analysis.cpp : 定义控制台应用程序的入口点。//#include "stdio.h"#include "stdlib.h"#include "string.h"#include "iostream"using namespace std;//词法分析程序//首先定义种别码/*第一类：标识符 letter(letter | digit)* 无穷集第二类：常数 (digit)+ 无穷集第三类：保留字(32)auto break casechar constcontinuedefault do double else enum externfloatforgotoifint longregister return short signedsizeofstaticstructswitch typedef union unsigned voidvolatile while第四类：界符 ‘/*’、‘//’、 () { } [ ] " " '第五类：运算符 <、<=、>、>=、=、+、-、*、/、^、对所有可数符号进行编码：<$,0><auto,1>...<while,32><+，33><-,34><*,35></,36><<,37><<=,38><>,39><>=,40><=,41><==,42><!=,43><;,44><(,45><),46><^,47><,,48><",49><',50><#,51><&,52><&&,53><|,54><||,55><%,56><~,57><<<,58>左移<>>,59>右移<[,60><],61><{,62><},63><\,64><.,65><?,66><:,67><!,68>"[","]","{","}"<常数99 ,数值><标识符100 ，标识符指针>*//****************************************************************************************///全局变量，保留字表static char reserveWord[32][20] = {"auto", "break", "case", "char", "const", "continue","default", "do", "double", "else", "enum", "extern","float", "for", "goto", "if", "int", "long","register", "return", "short", "signed", "sizeof", "static","struct", "switch", "typedef", "union", "unsigned", "void","volatile", "while"};//界符运算符表,根据需要可以自行增加static char operatorOrDelimiter[36][10] = {"+", "-", "*", "/", "<", "<=", ">", ">=", "=", "==","!=", ";", "(", ")", "^", ",", "\"", "\'", "#", "&","&&", "|", "||", "%", "~", "<<", ">>", "[", "]", "{","}", "\\", ".", "\?", ":", "!"};static char IDentifierTbl[1000][50] = { "" };//标识符表/****************************************************************************************//********查找保留字*****************/int searchReserve(char reserveWord[][20], char s[]){for (int i = 0; i < 32; i++){if (strcmp(reserveWord[i], s) == 0){//若成功查找，则返回种别码return i + 1;//返回种别码}}return -1;//否则返回-1，代表查找不成功，即为标识符}/********查找保留字*****************//*********************判断是否为字母********************/bool IsLetter(char letter){//注意C语言允许下划线也为标识符的一部分可以放在首部或其他地方if (letter >= 'a'&&letter <= 'z' || letter >= 'A'&&letter <= 'Z'|| letter=='_'){return true;}else{return false;}}/*********************判断是否为字母********************//*****************判断是否为数字************************/bool IsDigit(char digit){if (digit >= '0'&&digit <= '9'){return true;}else{return false;}}/*****************判断是否为数字************************//********************编译预处理，取出无用的字符和注释**********************/void filterResource(char r[], int pProject){char tempString[10000];int count = 0;for (int i = 0; i <= pProject; i++){if (r[i] == '/'&&r[i + 1] == '/'){//若为单行注释“//”,则去除注释后面的东西，直至遇到回车换行while (r[i] != '\n'){i++;//向后扫描}}if (r[i] == '/'&&r[i + 1] == '*'){//若为多行注释“/* 。。。*/”则去除该内容i += 2;while (r[i] != '*' || r[i + 1] != '/'){i++;//继续扫描if (r[i] == '$'){printf("注释出错，没有找到 */，程序结束！！！\n");exit(0);}}i += 2;//跨过“*/”}if (r[i] != '\n'&&r[i] != '\t'&&r[i] != '\v'&&r[i] != '\r'){//若出现无用字符，则过滤；否则加载tempString[count++] = r[i];}}tempString[count] = '\0';strcpy(r, tempString);//产生净化之后的源程序}/********************编译预处理，取出无用的字符和注释**********************//****************************分析子程序，算法核心***********************/void Scanner(int &syn, char resourceProject[], char token[], int &pProject){//根据DFA的状态转换图设计int i, count = 0;//count用来做token[]的指示器，收集有用字符char ch;//作为判断使用ch = resourceProject[pProject];while (ch == ' '){//过滤空格，防止程序因识别不了空格而结束pProject++;ch = resourceProject[pProject];}for (i = 0; i<20; i++){//每次收集前先清零token[i] = '\0';}if (IsLetter(resourceProject[pProject])){//开头为字母token[count++] = resourceProject[pProject];//收集pProject++;//下移while (IsLetter(resourceProject[pProject]) || IsDigit(resourceProject[pProject])){//后跟字母或数字token[count++] = resourceProject[pProject];//收集pProject++;//下移}//多读了一个字符既是下次将要开始的指针位置token[count] = '\0';syn = searchReserve(reserveWord, token);//查表找到种别码if (syn == -1){//若不是保留字则是标识符syn = 100;//标识符种别码}return;}else if (IsDigit(resourceProject[pProject])){//首字符为数字while (IsDigit(resourceProject[pProject])){//后跟数字token[count++] = resourceProject[pProject];//收集pProject++;}//多读了一个字符既是下次将要开始的指针位置token[count] = '\0';syn = 99;//常数种别码}else if (ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == ';' || ch == '(' || ch == ')' || ch == '^'|| ch == ',' || ch == '\"' || ch == '\'' || ch == '~' || ch == '#' || ch == '%' || ch == '['|| ch == ']' || ch == '{' || ch == '}' || ch == '\\' || ch == '.' || ch == '\?' || ch == ':'){//若为运算符或者界符，查表得到结果token[0] = resourceProject[pProject];token[1] = '\0';//形成单字符串for (i = 0; i<36; i++){//查运算符界符表if (strcmp(token, operatorOrDelimiter[i]) == 0){syn = 33 + i;//获得种别码，使用了一点技巧，使之呈线性映射break;//查到即推出}}pProject++;//指针下移，为下一扫描做准备return;}else if (resourceProject[pProject] == '<'){//<,<=,<<pProject++;//后移，超前搜索if (resourceProject[pProject] == '='){syn = 38;}else if (resourceProject[pProject] == '<'){//左移pProject--;syn = 58;}else{pProject--;syn = 37;}pProject++;//指针下移return;}else if (resourceProject[pProject] == '>'){//>,>=,>>pProject++;if (resourceProject[pProject] == '='){syn = 40;}else if (resourceProject[pProject] == '>'){syn = 59;}else{pProject--;syn = 39;}pProject++;return;}else if (resourceProject[pProject] == '='){//=.==pProject++;if (resourceProject[pProject] == '='){syn = 42;}else{pProject--;syn = 41;}pProject++;return;}else if (resourceProject[pProject] == '!'){//!,!=pProject++;if (resourceProject[pProject] == '='){syn = 43;}else{syn = 68;pProject--;}pProject++;return;}else if (resourceProject[pProject] == '&'){//&,&&pProject++;if (resourceProject[pProject] == '&'){syn = 53;}else{pProject--;syn = 52;}pProject++;return;}else if (resourceProject[pProject] == '|'){//|,||pProject++;if (resourceProject[pProject] == '|'){syn = 55;}else{pProject--;syn = 54;}pProject++;return;}else if (resourceProject[pProject] == '$'){//结束符syn = 0;//种别码为0}else{//不能被以上词法分析识别，则出错。printf("error：there is no exist %c \n", ch);exit(0);}}int main(){//打开一个文件，读取其中的源程序char resourceProject[10000];char token[20] = { 0 };int syn = -1, i;//初始化int pProject = 0;//源程序指针FILE *fp, *fp1;if ((fp = fopen("G:\\demo_src.txt", "r")) == NULL){//打开源程序cout << "can't open this file";exit(0);}resourceProject[pProject] = fgetc(fp);while (resourceProject[pProject] != '$'){//将源程序读入resourceProject[]数组pProject++;resourceProject[pProject] = fgetc(fp);}resourceProject[++pProject] = '\0';fclose(fp);cout << endl << "源程序为:" << endl;cout << resourceProject << endl;//对源程序进行过滤filterResource(resourceProject, pProject);cout << endl << "过滤之后的程序:" << endl;cout << resourceProject << endl;pProject = 0;//从头开始读if ((fp1 = fopen("G:\\demo_compile.txt", "w+")) == NULL){//打开源程序cout << "can't open this file";exit(0);}while (syn != 0){//启动扫描Scanner(syn, resourceProject, token, pProject);if (syn == 100){//标识符for (i = 0; i<1000; i++){//插入标识符表中if (strcmp(IDentifierTbl[i], token) == 0){//已在表中break;}if (strcmp(IDentifierTbl[i], "") == 0){//查找空间strcpy(IDentifierTbl[i], token);break;}}printf("(标识符 ,%s)\n", token);fprintf(fp1, "(标识符 ,%s)\n", token);}else if (syn >= 1 && syn <= 32){//保留字printf("(%s , --)\n", reserveWord[syn - 1]);fprintf(fp1, "(%s , --)\n", reserveWord[syn - 1]);}else if (syn == 99){//const 常数printf("(常数 , %s)\n", token);fprintf(fp1, "(常数 , %s)\n", token);}else if (syn >= 33 && syn <= 68){printf("(%s , --)\n", operatorOrDelimiter[syn - 33]);fprintf(fp1, "(%s , --)\n", operatorOrDelimiter[syn - 33]);}}for (i = 0; i<100; i++){//插入标识符表中printf("第%d个标识符： %s\n", i + 1, IDentifierTbl[i]);fprintf(fp1, "第%d个标识符： %s\n", i + 1, IDentifierTbl[i]);}fclose(fp1);return 0;}
