標識符

letter(letter|digit)*

letter->A|B|…|Z|a|b|…|z

digit->0|1|2|3|4|…|9

十進制整數

0 | (1|2|3|4|5|6|7|8|9)(0|1|2|3|4|5|6|7|8|9)^*

八進制整數

0(1|2|3|4|5|6|7)(0|1|2|3|4|5|6|7)^*

十六進制整數

0x(0|1|2|3|4|5|6|7|8|9|a|b|c|d|e|f)(0|1|2|3|4|5|6|7|8|9|a|b|c|d|e|f)^*

運算符和分隔符

+ ?- ?* ?/ ?>? <? =? (? ) ?；

關鍵字

if? then? else? while? do ?

標識符??????????

正規式?

id->letter(letter|digit)*

letter->A|B|…|Z|a|b|…|z

digit->0|1|2|3|4|…|9

正規文法

S->aB’|bB’|…|zB’|AB’|BB’|…|ZB’

B’->0B’|1B’|…|9B’

狀態圖

八進制整數?????????????

正規式?

0(1|2|3|4|5|6|7)(0|1|2|3|4|5|6|7)^*

正規文法

S->01B|02B|…|07B

B->0B|1B|…|7B|

十進制整數?????????????

正規式?

0 | (1|2|3|4|5|6|7|8|9)(0|1|2|3|4|5|6|7|8|9)^*

正規文法

S->0|1B|2B|…|9B

B->0B|1B|…|9B|

十六進制整數?????????????

正規式?

0x(0|1|2|3|4|5|6|7|8|9|a|b|c|d|e|f)(0|1|2|3|4|5|6|7|8|9|a|b|c|d|e|f)^*

正規文法

S->0(x|X)(1B’|2B’|…|9B’|aB’|bB’|…|fB’|AB’|…|FB’)

B’->0B’|1B’|…|7B’|

識別這三種數字的狀態圖

運算符和分隔符

狀態圖

//對外函數

extern void initLexer();//打開文件，初始化詞法分析器

extern int nextToken();//獲得一個token

//對外變量

extern int attr=-1;//是數值的時候存儲數值，是標識符時存儲在名字表中的位置

extern int lineNo=1;//顯示行數

extern char *keyWord[]={

??????? "if",

??????? "else",

??????? "then",

??????? "while",

??? ????"do"

};

//內部函數

static int fail();//換狀態圖

static char getAnChar();//在文件中讀取一個字符，指針下移一位

static void ungetAnChar();//在文件中指針回退一位

static void getNum(int type);//根據type，獲得十進制數值，存儲在attr

static int lookup(const char *s);//在符號表中查找ID

static int insert(const char *s);//返回再符號表中的下標位置

static int isKeyWord(char word[]);//判斷是否為關鍵字

//內部變量

static char lexBuf[100];//字符緩存，用來存儲當前分析的字

static int state=1, start=1;//當前狀態和狀態表的開始狀態

static int currentPos=0;//文件中當前指針的位置

static int tokenBeginning=0;//進入一個狀態表時指針位置，即換狀態表時的回退位置。

static FILE *fp;//被編譯的文件指針

static int smptableLength=0;//當前符號表的長度

int nextToken(){

?

??? int length=0;

??? char c;

??? int keyWordPos=0;//在關鍵字數組中的下標

?

??? state=1;start=1;

??? //存儲開始位置

??? tokenBeginning=currentPos;

??? //狀態圖的實現

??? while(1){

?

??????? switch(state){

??????? case 1:

??????????? c=getAnChar();

??????????? if(c==' '||c=='/t'||c=='/r'){

??????????????? tokenBeginning++;

??????????? }

??????????? else if(c=='/n'){

??????????????? lineNo++;

??????????????? tokenBeginning++;

??????????? }

??????????? else if(isalpha(c)){

??????????????? state=2;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else if(c==EOF) return FILEEND;

??????????? else state=fail();

??????????? break;

??????? case 2:

????????? ??c=getAnChar();

??????????? if(isdigit(c)||isalpha(c)){

??????????????? state=2;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else state=3;

??????????? break;

??????? case 3:

??????????? ungetAnChar();

??????????? lexBuf[length]='/0';

?? ?????????keyWordPos=isKeyWord(lexBuf);

??????????? if(keyWordPos!=-1){

??????????????? //是關鍵字

??????????????? return IF+keyWordPos;

??????????? }

??????????? //不是關鍵字

??????????? attr=insert(lexBuf);//把ID在名字表中的數組下標存儲在attr中

??????????? return ID;

??????? case 4:

??????????? c=getAnChar();

??????????? if(c=='0') state=5;

??????????? else if(c>='1' && c<='9'){

??????????????? state=12;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else state=fail();

??????????? break;

??????? case 5:

?????????? ?c=getAnChar();

??????????? if(c=='x') state=6;

??????????? else if(c>='1'&& c<='8'){

??????????????? state=10;

??????????????? lexBuf[length++]=c;

??????????? }

?

??????????? else state=13;

??????????? break;

??????? case 6:

??????????? c=getAnChar();

??? ????????if(c>='1' && c<='9' || c>='a'&& c<='f' || c>='A' && c<='B'){

??????????????? state=7;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else state=fail();

??????????? break;

??????? case 7:

??????????? c=getAnChar();

??????????? if(c>='1' && c<='9' || c>='a'&& c<='f' || c>='A' && c<='B'||c=='0'){

??????????????? state=7;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else state=8;

??????????? break;

??????? case 8:

??????????? ungetAnChar();

??????????? lexBuf[length]='/0';

??????????? getNum(INT16);//把數值存在attr中

??????????? return INT16;

??????? case 10:

??????????? c=getAnChar();

??????????? if(c>='0'&& c<='8'){

??????????????? state=10;

??????????????? lexBuf[length++]=c;

??????????? }

??????????? else state=11;

???????? ???break;

??????? case 11:

?? ?????????ungetAnChar();

??????????? lexBuf[length]='/0';

??????????? getNum(INT8);//把數值存在attr中

??????????? return INT8;

??????? case 12:

??????????? c=getAnChar();

??????????? if(c>='0' && c<='9'){

??????????????? state=12;

? ??????????????lexBuf[length++]=c;

??????????? }

??????????? else state=13;

??????????? break;

??????? case 13:

??????????? ungetAnChar();

??????????? lexBuf[length]='/0';

??????????? getNum(INT10);//把數值存在attr中

??????????? return INT10;

??????? case 14:

?? ?????????c=getAnChar();

??????????? if(c=='+') state=15;

??????????? else if(c=='-') state=16;

??????????? else if(c=='*') state=17;

??????????? else if(c=='/') state=18;

??????????? else if(c=='>') state=19;

??????????? else if(c=='<') state=20;

???????? ???else if(c=='=') state=21;

??????????? else if(c=='(') state=22;

??????????? else if(c==')') state=23;

??????????? else if(c==';') state=24;

??????????? else state=fail();

??????????? break;

??????? case 15:

??????????? return ADD;

??????? case 16:

???? ???????return SUB;

??????? case 17:

??????????? return MUL;

??????? case 18:

??????????? return DIV;

??????? case 19:

??????????? return GT;

??????? case 20:

??????????? return LT;

??????? case 21:

??????????? return EQ;

??????? case 22:

??????????? return LBR;

??????? case 23:

??????????? return RBR;

??????? case 24:

??????????? return SEM;

??????? }

??? }????

}

void main(){

???? int token;

???? int oldLine=-1;

???? initLexer();??

?????

???? while(1){

???????? token=nextToken();

???? ????if(token==FILEEND) break;

???????? if(oldLine!=lineNo) {

???????????? printf("___________Line %d____________/n",lineNo);

???????????? oldLine=lineNo;

???????? }

????????

??????? if(token==ID){//標識符

??????????? printf("ID:%d,Pos:%d/n",token,attr);

??? ????}

??????? else {

??????????? switch(token){

??????????????? case INT16:case INT8:case INT10://數字

??????????????????? printf("%d/t/t%d/n",token,attr);

??????????????????? break;

??????????????? default: printf("%d/n",token);//關鍵字

??????????????? }

???? ???}

??????? token=nextToken();

???? }

}//*/

??? 1? 92+data>? 0x3f? 04? while

1x3 x3 x3 x44?? 00

while (1) do num=10;

num=11;

if (1) then caoning=0x11;

if (1) than caoning=878;

struct ENTYE{

?? char word[100];

?? float value;

};

int smptableLength=0;

struct ENTYE smptable[200];

/*查找s在符號表的位置，沒有返回-1*/

int lookup(const char *s){

??? int i;

??? for (i=0;i<smptableLength;i++){

??????? if (strcmp(smptable[i].word,s)==0) return i;

??? }

??? return -1;

}

/*返回s在符號表中的位置*/

int insert(const char *s){

?? int i=lookup(s);

?? if(i==-1){

??????? strcpy(smptable[smptableLength].word,s)；

?????? //smptableLength++;

?????? return smptableLength++;

?? }

?? return i;

}

輸入\狀態

D0_3

D4_7

D8_9

S_a

S_b

S_c

S_d

S_f

Other

Cbegin

(Abegin,Begin)

A1

A1,B1

B1

輸入\狀態

D0_3

D4_7

D8_9

S_a

S_b

S_c

S_d

S_f

Other

Cbegin

(Abegin,Begin)

A1

A1,B1

B1

C1

(A1,B1)

A1

A1,B1

B1

A2,B2

輸入\狀態

D0_3

D4_7

D8_9

S_a

S_b

S_c

S_d

S_f

Other

Cbegin

(Abegin,Begin)

A1

A1,B1

B1

C1

(A1,B1)

A1

A1,B1

B1

A2,B2

C2

(A2,B2)

A3

B3