0916 编程实验一 词法分析程序

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

#define _KEY_WOED_END "waiting for your expanding" //关键字结束标志

typedef struct

{

int typenum;

char * word;

}WORD;

char input[255];

char token[255]=""; 

int p_input; 

int p_token;

char ch; //当前所读的字符

char *rwtab[]={"begin","if","then","while","do","end",_KEY_WOED_END}; //C语言关键字

WORD * scaner(); //词法扫描函数，获得关键字

main()

int over=1;

WORD *oneword;

oneword=(WORD *)malloc(sizeof(WORD));

printf("请输入您的单词（以#作为结束标志）:");

scanf("%[^#]s",input); //读入源程序字符串到缓冲区，以#结束，允许多行输入

p_input=0;

printf("您输入的单词是:%s\n\n",input);

while(over<1000&&over!=-1)

{

oneword=scaner();

printf("(%d,%s)",oneword->typenum,oneword->word);

over=oneword->typenum;

}

printf("\n按#可推出程序");

scanf("%[^#]s",input);

}

//需要用到的自编函数参考实现

//从输入缓冲区读取一个字符到ch中

char m_getch(){

ch=input[p_input];

p_input=p_input+1;

return (ch);

//去掉空白字符

void getbc()

while(ch==' '||ch==10){

//拼接单词

void concat()

token[p_token]=ch;

p_token=p_token+1;

token[p_token]='\0';

//判断是否字母

int letter()

if(ch>='a'&&ch<='z'||ch>='A'&&ch<='Z')return 1;

else return 0;

//判断是否数字

int digit()

if(ch>='0'&&ch<='9')

return 1;

else

return 0;

//检索关键字表格

int reserve()

int i=0;

for(i=0;i<7;i++)

if(!strcmp(rwtab[i],token))

{

return i+1;

}

i=i+1;

return 10;

//回退一个字符

void retract()

p_input=p_input-1;

/*数字转换成二进制

char *dtb()

return NULL;

*/

WORD *scaner()

WORD *myword;

myword=(WORD *)malloc(sizeof(WORD));

myword->typenum=10;

myword->word="";

p_token=0;

m_getch();

getbc();

if(letter())

while(letter()||digit())

concat();

m_getch();

retract();

myword->typenum=reserve();

myword->word=token;

return(myword);

else if(digit())

while(digit())

concat();

m_getch();

myword->typenum=20;

return(myword);

switch(ch)

case '=':m_getch();

if(ch=='=')

{

myword->typenum=39;

myword->word="==";

return(myword);

}

retract();

myword->typenum=21;

myword->word="=";

return(myword);

break;

case '+':

myword->typenum=22;

myword->word="+";

break;

case '-':

myword->typenum=23;

myword->word="-";

case '*':

myword->typenum=24;

myword->word="*";

break;

case '/':

myword->typenum=25;

myword->word="/";

case '(':

myword->typenum=26;

myword->word="(";

case ')':

myword->typenum=27;

myword->word=")";

case '[':

myword->typenum=28;

myword->word="[";

case ']':

myword->typenum=29;

myword->word="]";

case '{':

myword->typenum=30;

myword->word="{";

case '}':

myword->typenum=31;

myword->word="}";

case ',':

myword->typenum=32;

myword->word=",";

case ':':

myword->typenum=33;

myword->word=":";

case ';':

myword->typenum=34;

myword->word=";";

case '>':

myword->typenum=35;

myword->word=">";

case '<':

myword->typenum=36;

myword->word="<";

case '!':

myword->typenum=40;

myword->word="!=";

return(myword);

myword->typenum=-1;

myword->word="ERROR";

case '\0':

myword->typenum=1000;

myword->word="OVER";

default: