刚学编译原理，老师让写的一个简单的词法分析器1.0，以后可能有改进
#include<stdio.h> #include<stdlib.h> char yytext[256]; int line = 1,row = 0,rows = 0; int IsLetter(char ch) { if((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')) return 1; else return 0; } int IsDigit(char ch) { if(ch >= '0' && ch <='9') return 1; else return 0; } int KeyWord() { char data[256]; FILE *Key; Key = fopen("keyword.txt","r"); if(Key == NULL) { printf("打开keyword文件失败！\n"); return -1; } while(fscanf(Key,"%s ",data)!=EOF) { if(strcmp(yytext,data) == 0) { fclose(Key); return 1; } } fclose(Key); return 0; } int Scan(FILE * fp) { char in; in = fgetc(fp); row ++; rows = row; while(in == ' ' || in == '\n') { if(in == '\n') { line ++; row = 0; } in = fgetc(fp); row ++; rows = row; } if(in == EOF) return 0; if(IsLetter(in) || in == '$') { int i = 0; yytext[i] = in; i++; in = fgetc(fp); row ++; while(IsLetter(in) || IsDigit(in) || in == '$') { yytext[i] = in; i ++; in = fgetc(fp); row ++; } yytext[i] = '\0'; i ++; ungetc(in,fp); row --; if(KeyWord(yytext)) return 1; else return 2; } else if(IsDigit(in)) { int i = 0; yytext[i] = in; i ++; in = fgetc(fp); row ++; while(IsDigit(in)) { yytext[i] = in; i ++; in = fgetc(fp); row ++; } if(in == '.') { yytext[i] = in; i ++; in = fgetc(fp); row ++; while(IsDigit(in)) { yytext[i] = in; i ++; in = fgetc(fp); row ++; } yytext[i] = '\0'; i ++; ungetc(in,fp); row --; return 4; } yytext[i] = '\0'; i ++; ungetc(in,fp); row --; return 3; } else if(in == '\"') { int i = 0; yytext[i] = in; i ++; in = fgetc(fp); row ++; while(in != '\"') { if(in == '\n') { line ++; row = 0; } yytext[i] = in; in = fgetc(fp); row ++; } yytext[i] = '\0'; i ++; ungetc(in,fp); row --; return 5; } else if(in == '\'') { int i = 0; yytext[i] = in; i ++; in = fgetc(fp); row ++; yytext[i] = in; i ++; in = fgetc(fp); if(in != '\'') return -1; yytext[i] = in; i ++; return 6; } else if(in == '{' || in == '}' || in == '(' || in == ')' || in == ';' || in == ',') { int i = 0; yytext[i] = in; i ++; return 7; } else if(in == '=') { int i = 0; yytext[i] = in; i ++; in = fgetc(fp); row ++; if(in == '=' || in == '<' || in == '>') { yytext[i] = in; i ++; return 8; } if(in != '=') { ungetc(in,fp); row --; return 8; } } else if(in == '+' || in == '-' || in =='*' || in == '/') { int i = 0; yytext[i] = in; i ++; return 8; } else { int i = 0; yytext[i] = in; i ++; return -1; } return 0; } int main() { char c; int re,i; FILE *yyin; yyin = fopen("test.txt","r"); if(yyin == NULL) { printf("打开文件失败，test.txt可能不存在\n"); return 0; } while((c = fgetc(yyin)) != EOF) { ungetc(c,yyin); re = Scan(yyin); if(re != -1 && re != 0) printf("%s 类型:%d 位置:Line - Row -\n",yytext,re,line,rows); else if (re == -1) printf("%s Error\n",yytext); else printf("finished.\n"); for(i = 0; yytext[i] != '\0'; i ++) yytext[i] = '\0'; } fclose(yyin); return 0; }