#include <string>
using namespace std
string key[6] = {"begin", "if", "then", "while", "do", "end"}
//关键字
bool isKey( string str, int &syn) //判断是否为关键字，若是传回相
应关键码的种别名
{
int i
for(i=0i<6i++)
{
if(str == key[i])
{
syn = i + 1
return true
}
}
return false
}
bool isLetter(char c) //是否为字母
{
if((c >= 'A' &&c <= 'Z') || (c >= 'a' &&c <= 'z'))
return true
else
return false
}
bool isDigit(char c) //是否为数字
{
if(c >= '0' &&c <= '9')
return true
else
return false
}
void analyse(FILE *fileP)
{
int n
char c
string str = ""
while((c = fgetc(fileP)) != EOF)
{
if(c == ' ' || c == '\n' || c == '\t')
continue
else if(isDigit(c)) //数字
{
while(isDigit(c))
{
str += c
c = fgetc(fileP)
}
fseek(fileP, -1, SEEK_CUR)
cout <<"(11, " <<str <<")" <<endl
str = ""
}
else if(isLetter(c)) //字母开头的
{
while(isDigit(c) || isLetter(c))
{
str += c
c = fgetc(fileP)
}
fseek(fileP, -1, SEEK_CUR)
if(isKey(str, n))
cout <<"(" <<n <<", " <<str <<")" <<endl//关键码
else
cout <<"(10, " <<"\'"<<str <<"\'" <<")" <<endl//标志符
str = ""
}
else // *** 作符等
{
switch(c)
{
case '+':
cout <<"(13, +)" <<endl
break
case '-':
cout <<"(14, -)" <<endl
break
case '*':
cout <<"(15, *)" <<endl
break
case '/':
cout <<"(16, /)" <<endl
break
case ':':
{
if(c=fgetc(fileP) == '=')
cout <<"(18, :=)" <<endl
else
{
cout <<"(17, :)" <<endl
fseek(fileP, -1, SEEK_CUR)
}
break
}
case '<':
{
c=fgetc(fileP)
if(c == '=')
cout <<"(22, <=)" <<endl
else if(c == '>')
cout <<"(21, <>)" <<endl
else
{
cout <<"(20, <)" <<endl
fseek(fileP, -1, SEEK_CUR)
}
break
}
case '>':
{
c=fgetc(fileP)
if(c == '=')
cout <<"(24, >=)" <<endl
else
{
cout <<"(23, >)" <<endl
fseek(fileP, -1, SEEK_CUR)
}
break
}
case '=':
cout <<"(25, =)" <<endl
break
case '':
cout <<"(26, )" <<endl
break
case '(':
cout <<"(27, ()" <<endl
break
case ')':
cout <<"(28, ))" <<endl
break
case '#':
cout <<"(0, #)" <<endl
break
}
}
}
}
int main()
{
FILE *fileP
fileP = fopen("test.txt", "r")
cout <<"------词法分析如下------" <<endl
analyse(fileP)
return 0
}
#include "stdio.h" /*定义I/O库所用的某些宏和变量*/
#include "string.h" /*定义字符串库函数*/
#include "conio.h" /*提供有关屏幕窗口 *** 作函数*/
#include "ctype.h" /*分类函数*/
char prog[80]={'\0'},
token[8] /*存放构成单词符号的字符串*/
char ch
int syn, /*存放单词字符的种别码*/
n,
sum, /*存放整数型单词*/
m,p /*p是缓冲区prog的指针，m是token的指针*/
char *rwtab[6]={"begin","if","then","while","do","end"}
void scaner(){
m=0
sum=0
for(n=0n<8n++)
token[n]='\0'
ch=prog[p++]
while(ch==' ')
ch=prog[p++]
if(isalpha(ch)) /*ch为字母字符*/{
while(isalpha(ch)||isdigit(ch)) /*ch 为字母字符或者数字字符*/{
token[m++]=ch
ch=prog[p++]}
token[m++]='\0'
ch=prog[p--]
syn=10
for(n=0n<6n++)
if(strcmp(token,rwtab[n])==0) /*字符串的比较*/{
syn=n+1
break}}
else
if(isdigit(ch)) /*ch是数字字符*/{
while(isdigit(ch)) /*ch是数字字符*/{
sum=sum*10+ch-'0'
ch=prog[p++]}
ch=prog[p--]
syn=11}
else
switch(ch){
case'<':m=0token[m++]=chch=prog[p++]
if(ch=='>'){
syn=21
token[m++]=ch}
else if(ch=='='){
syn=22
token[m++]=ch}
else{
syn=20
ch=prog[p--]}
break
case'>':m=0token[m++]=chch=prog[p++]
if(ch=='='){
syn=24
token[m++]=ch}
else{
syn=23
ch=prog[p--]}
break
case':':m=0token[m++]=chch=prog[p++]
if(ch=='='){
syn=18
token[m++]=ch}
else{
syn=17
ch=prog[p--]}
break
case'+':syn=13token[0]=chbreak
case'-':syn=14token[0]=chbreak
case'*':syn=15token[0]=chbreak
case'/':syn=16token[0]=chbreak
case'=':syn=25token[0]=chbreak
case'':syn=26token[0]=chbreak
case'(':syn=27token[0]=chbreak
case')':syn=28token[0]=chbreak
case'#':syn=0token[0]=chbreak
default:syn=-1}}
main()
{
printf("\n\nThe significance of the figures:\n"
"1.figures 1 to 6 said Keyword\n"
"2.figures 10 and 11 said Other indicators\n"
"3.figures 13 to 28 said Operators\n")
p=0
printf("\nplease input string:\n")
do {
ch=getchar()
prog[p++]=ch
}while(ch!='#')
p=0
do{
scaner()
switch(syn){
case 11: printf("(%d,%d)\n",syn,sum)break
case -1: printf("\n ERROR\n")break
default: printf("(%d,%s)\n",syn,token)
}
}while(syn!=0)
getch()
}
程序测试结果
对源程序begin x:=9: if x>9 then x:=2*x+1/3 end #的源文件，经过词法分析后输出如下图5-1所示：
具体的你在修改修改吧
这是我们实验的作业，代码如下：#include <iostream>
#include<string>
using namespace std
#define MAX 22
char ch =' '
string key[15]={"begin","end","if","then","else","while","write","read",
"do", "call","const","char","until","procedure","repeat"}
int Iskey(string c){ //关键字判断
int i
for(i=0i<MAXi++) {
if(key[i].compare(c)==0) return 1
}
return 0
}
int IsLetter(char c) {//判断是否为字母
if(((c<='z')&&(c>='a'))||((c<='Z')&&(c>='A'))) return 1
else return 0
}
int IsDigit(char c){ //判断是否为数字
if(c>='0'&&c<='9') return 1
else return 0
}
void analyse(FILE *fpin){
string arr=""
while((ch=fgetc(fpin))!=EOF) {
arr=""
if(ch==' '||ch=='\t'||ch=='\n'){}
else if(IsLetter(ch)){
while(IsLetter(ch)||IsDigit(ch)) {
if((ch<='Z')&&(ch>='A')) ch=ch+32
arr=arr+ch
ch=fgetc(fpin)
}
fseek(fpin,-1L,SEEK_CUR)
if (Iskey(arr)){cout<<arr<<"\t$关键字"<<endl}
else cout<<arr<<"\t$普通标识符"<<endl
}
else if(IsDigit(ch)){
while(IsDigit(ch)||ch=='.'&&IsDigit(fgetc(fpin))){
arr=arr+ch
ch=fgetc(fpin)
}
fseek(fpin,-1L,SEEK_CUR)
cout<<arr<<"\t$无符号实数"<<endl
}
else switch(ch){
case'+':
case'-' :
case'*' :
case'=' :
case'/' :cout<<ch<<"\t$运算符"<<endlbreak
case'(' :
case')' :
case'[' :
case']' :
case'' :
case'.' :
case',' :
case'{' :
case'}' :cout<<ch<<"\t$界符"<<endlbreak
case':' :{ch=fgetc(fpin)
if(ch=='=') cout<<":="<<"\t$运算符"<<endl
else {cout<<"="<<"\t$运算符"<<endl
fseek(fpin,-1L,SEEK_CUR)}
}break
case'>' :{ch=fgetc(fpin)
if(ch=='=') cout<<">="<<"\t$运算符"<<endl
if(ch=='>')cout<<">>"<<"\t$输入控制符"<<endl
else {cout<<">"<<"\t$运算符"<<endl
fseek(fpin,-1L,SEEK_CUR)}
}break
case'<' :{ch=fgetc(fpin)
if(ch=='=')cout<<"<="<<"\t$运算符"<<endl
else if(ch=='<')cout<<"<<"<<"\t$输出控制符"<<endl
else if(ch=='>') cout<<"<>"<<"\t$运算符"<<endl
else{cout<<"<"<<"\t$运算符"<<endl
fseek(fpin,-1L,SEEK_CUR)}
}break
default : cout<<ch<<"\t$无法识别字符"<<endl
}
}
}
void main(){
char in_fn[30]
FILE * fpin
cout<<"请输入源文件名（包括路径和后缀名）:"
for(){
cin>>in_fn
if((fpin=fopen(in_fn,"r"))!=NULL) break
else cout<<"文件路径错误！请输入源文件名（包括路径和后缀名）:"
}
cout<<"\n********************分析如下*********************"<<endl
analyse(fpin)
fclose(fpin)
}
自己写一个源文件，TXT格式的，简单的几个句子就可以！
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