我有这个项目，我需要编写代码来模拟DFA以接受url。我发现的DFA部分完全没问题，但是我的代码存在一些问题。 第一个问题是，当我运行代码时，似乎没有超过cout＆lt;＆lt;“输入y / n部分。 第二个可能是它的一部分，但我得到了很多
27逗号运算符的左操作数无效[-Wunused-value]
27逗号运算符的右操作数无效[-Wunused-value]
27错误：预期';'在'）'令牌之前
31错误：在'goto'之前预期的primary-expression
31错误：预期'）'在'goto'之前
在每个for循环中出于某种原因
#include <iostream>
#include <string.h>
#include <stdlib.h>
using namespace std;
int main() {
char asdf='y';
string str;
int stringlength,state;
while (asdf=='y'){
start:
cout << "Do you want to enter a string?(y/n)\n";
cin >> asdf;
cout << "Enter the string:\n";
cin >> str;
stringlength=str.size();
state=0;
//transition states q0 start
//w means goto q1,increment state by 1
if(str[0]=='w'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q1;
}
//. means trap state,loop the rest of the char's and output trap state and output "rejected", then return to start
if(str[0]=='.'){
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
}
//not w and not . means goto q7
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q7;
q1:
//w means goto q2
if (str[1]=='w'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q2;
}
//. means go to q6
if (str[1]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q6;
}
//not w and not . means goto q7
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q7;
q2:
//w means goto q3
if (str[2]=='w'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q3;
}
//. means go to q6
if (str[2]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q6;
}
//not w and not . means goto q7
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q7;
q3:
//w means goto q3
if (str[3]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q4;
}
//not . means goto q7
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q7;
q4:
//. mean trap state
if (str[4]=='.'){
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
}
//everything else goes to q5
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q5;
q5:
//. means goto q6
if (str[state]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q6;
}
//everything else goes back to q5
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q5;
q6:
//c means goto q8
if (str[state]=='c'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q8;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q7:
//. means goto q6
if (str[state]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q6;
}
//everything else goes back to q7
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q7;
q8:
//o means goto q9
if (str[state]=='o'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q9;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q9:
//m means goto q10
if (str[state]=='m'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q10;
}
//. means goto q11
if (str[state]=='.'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q11;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q10:
//compare length of string to state,if it matches there are no more char in string and is accepted
if (stringlength==state){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
cout << "accepted\n";
goto start;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q11:
//j means goto q12
if (str[state]=='j'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q12;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q12:
//p means goto q13
if (str[state]=='p'){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
state++;
goto q13;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
q13:
//compare length of string to state,if it matches there are no more char in string and is accepted
if (stringlength==state){
cout << "character:"<<str[state]<<" "<<"state:"<<state<<"\n";
cout << "accepted\n";
goto start;
}
//everything else goes to trap state
state=stringlength-state;
for(state,state>0,state--){
cout << "character:"<<str[stringlength-state]<<" "<<"state:trap\n";
}
cout << "rejected\n";
goto start;
}
return 0;
}
答案 0 :(得分：2)
您需要使用分号而不是逗号分隔for循环中的三个表达式：
for(state,state>0,state--){
^-------^ Change these to ;