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無論是詞法分析，還是語法分析，給我的第一感覺就是邏輯要嚴謹。由于項目有自己一套完整的語言和語法，設計好其對應的詞法分析器和語法分析器顯得尤為重要。

這里給您提供一個免費的java詞法分析器下載

java詞法分析器實現原理步驟

先寫其正則式，然后NFA，然后DFA，然后對其進行優化，最后準備工作做好了，就可以開始寫代碼了。

    下面對其里面的主要函數進行講解：
enum Token_Type {
     keyword =1,              //關鍵字
     Identifier,            //標識符
     operatorr,             //運算符
     operatorrd,             //單運算符
     constant,              //常量
     escape,                //轉義符
     separator,              //界限符
     notype,                  //沒有類型
     zhushi                   //注釋類型
};

對其單詞的類型定義成枚舉。

typedef struct Token {
     Token_Type type; //其類型
     char *lexeme ;    //字符串
     int  value;       //屬性值
}Token;

//返回單詞的結構。

void InitScanner(char *ch){
     fp1 = fopen(ch,"r+");
     LineNo = 1;
}//初始化分析器。
void CloseScanner(){
     fclose(fp1);
}//關閉分析器
void EmptyTokenString(){
     memset(TokenBuffer,0,100);
}//清空緩沖區
static void AddCharTokenString(char Char)
{
    int TokenLenth=strlen(TokenBuffer);
    if(TokenLenth+1==sizeof(TokenBuffer)) return;
    TokenBuffer[TokenLenth]=Char;
    TokenBuffer[TokenLenth+1]='\0';
} //將一個字符添加到緩沖區
static char GetChar(){
     char Char;
     Char = fgetc(fp1);
     return Char;
}//從文件中讀取一個字符
static void BackChar(char Char) {
     if(Char!=EOF){
         ungetc(Char,fp1);
     }
}//將其字符后退一個。

static Token JudgeKeyToken(char *IDstring)；//這個函數實現對關鍵字進行判斷

下面是源代碼：

/************************************************************************
*                CopyRight@ice-snow studio                              *
*               email:bingxuefenggu@126.com                             *
*               qq: 405116890                                           *
************************************************************************/
//只考慮到整形常量
//實型沒考慮到
//需要解決轉義符如何描述的問題
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define TOKEN_LEN 100

enum Token_Type {
     keyword =1,              //關鍵字
     Identifier,            //標識符
     operatorr,             //運算符
     operatorrd,             //單運算符
     constant,              //常量
     escape,                //轉義符
     separator,              //界限符
     notype,                  //沒有類型
     zhushi                   //注釋類型
};
typedef struct Token {
     Token_Type type; //其類型
     char *lexeme ;    //字符串
     int  value;       //屬性值
}Token;
static Token Token_Tap[] = {
       {keyword,"abstract",0x103},
       {keyword,"boolean",0x103},
       {keyword,"break", 0x103},
       {keyword,"byte" ,0x103},
       {keyword,"case",0x103},
       {keyword,"catch",0x103},
       {keyword,"char", 0x103},
       {keyword, "class",0x103},
       {keyword,"const" ,0x103},
       {keyword,"continue" ,0x103},
       {keyword,"default" , 0x103},
       {keyword,"do",0x103},
       {keyword,"double",0x103},
       {keyword,"else",0x103},
       {keyword,"extends",0x103},
       {keyword,"false",0x103},
       {keyword,"final",0x103},
       {keyword,"finally",0x103},
       {keyword,"float",0x103},
       {keyword,"for",0x103},
       {keyword,"goto",0x103},
       {keyword,"if",0x103},
       {keyword,"implements",0x103},
       {keyword,"import",0x103},
       {keyword,"instanceof",0x103},
       {keyword,"int",0x103},
       {keyword,"interface",0x103},
       {keyword,"long",0x103},
       {keyword,"native",0x103},
       {keyword,"new",0x103},
       {keyword,"null",0x103},
       {keyword,"package",0x103},
       {keyword,"private",0x103},
       {keyword,"protected",0x103},
       {keyword,"public",0x103},
       {keyword,"return",0x103},
       {keyword,"short",0x103},
       {keyword,"static",0x103},
       {keyword,"super",0x103},
       {keyword,"switch",0x103},
       {keyword,"synchronized",0x103},
       {keyword,"this",0x103},
       {keyword,"throw",0x103},
       {keyword,"throws",0x103},
       {keyword,"transient",0x103},
       {keyword,"true",0x103},
       {keyword,"try", 0x103},
       {keyword,"void",0x103},
       {keyword,"volatile",0x103},
       {keyword,"while",0x103},
       {constant,"true",0x105},
       {constant,"false",0x105}
     //以上是所有的關鍵字
};
FILE *fp1;// 要讀文件的描述符
int LineNo;//單詞所在的行數
static char TokenBuffer[TOKEN_LEN];//單詞符號的緩存區
void InitScanner(char *ch){
     fp1 = fopen(ch,"r+");
     LineNo = 1;
}
void CloseScanner(){
     fclose(fp1);
}
void EmptyTokenString(){
     memset(TokenBuffer,0,100);
}
static void AddCharTokenString(char Char)
{
    int TokenLenth=strlen(TokenBuffer);
    if(TokenLenth+1==sizeof(TokenBuffer)) return;
    TokenBuffer[TokenLenth]=Char;
    TokenBuffer[TokenLenth+1]='\0';
}
static char GetChar(){
     char Char;
     Char = fgetc(fp1);
     return Char;
}
static void BackChar(char Char) {
     if(Char!=EOF){
         ungetc(Char,fp1);
     }
}
static Token JudgeKeyToken(char *IDstring){
     int loop;
     Token token;
     for(loop=0;loop<51;loop++){
         if(strcmp(Token_Tap[loop].lexeme,IDstring)==0)
         return Token_Tap[loop];
     }
     token.type = Identifier;
     //strcpy(token.lexeme,IDstring);//youwenti.
     token.lexeme = IDstring;
     token.value = 0x104;
     return token;
}