Invalid Conversion from char to string

Question

In my code, I made a string and I pushed that string to a stack. (I don't know if I did it correctly as I am new to C++ and the concept of stacks) But when I try to top (I think this outputs the first element in the stack) it doesn't work correctly. I get a conversion issue from char to string. Even if I cast it as char it doesn't work correctly. Is there some way to convert it? I am trying to get it to out put h.

I keep getting the error :

C:\main.cpp:15:37: error: invalid user-defined conversion from 'char' to 'std::stack >::value_type&& {aka std::basic_string&&}' [-fpermissive] nextWord.push(str[i + 1]);

#include <iostream>
#include <iomanip>
#include <map>
#include <string.h>
#include <stack>

using namespace std;

int main(){
std::stack<string> nextWord;
string str = "T<h>is is a test";

for(int i = 0; i < str.length(); i++){
    if (str[i + 2] == '>' && str[i] ==  '<'){
        nextWord.push(str[i + 1]);
    }
}
while (!nextWord.empty()) {
    cout << "String: " << nextWord.top();;
}

cout << nextWord.pop() << '>' ;
}

score 4 · Answer 1 · answered Dec 05 '15 at 06:01

In you code 3 problems:

nextWord.push(str[i+1]); You try to put char in the stack instead string. You need change the type of stack: stack<char> nextWord; or convert char to string before putting in the stack for example:
```
    string tmp = "";

    tmp += str[i+1];

    nextWord.push(tmp);
```

Endless cycle:

    while (!nextWord.empty()) {
     cout << "String: " << nextWord.top();
    }

stack.top() - just returns value in the top of the stack

to pass all the elements you need add calling stack.pop() in the body of cycle, for example:

    while (!nextWord.empty()) {
        cout << "String: " << nextWord.top();
        nextWord.pop();
    }

cout << nextWord.pop() << '>' ; The return type of the stack.pop() is void. You can not write like this.

AndersK · Answer 2 · 2015-12-05T05:44:31.410

1

stack::pop has return value void. In order to get the value from the stack use top and then call pop.

cout << nextWord.top() << ">";
nextWord.pop();

When you push strings you need to push the string, not a character i.e.

nextWord.push(str);

Also #include <string> instead of string.h

edited Dec 05 '15 at 05:44

answered Dec 05 '15 at 05:39

AndersK

35,813
6
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I have that there, but I keep getting this error : C:\Users\Victor\ClionProjects\Hw7\main.cpp:15:37: error: invalid user-defined conversion from 'char' to 'std::stack >::value_type&& {aka std::basic_string&&}' [-fpermissive] nextWord.push(str[i + 1]); – boboobobo Dec 05 '15 at 05:41
I'm sorry about these stupid questions, but where should I include ? – boboobobo Dec 05 '15 at 05:45
no question is stupid. instead of `#include ` write `#include ` also it is better to move your `using namespace std` inside your main function. `int main() { using namespace std; ... }` – AndersK Dec 05 '15 at 05:46
Ok thanks. But what I originally wanted to do was output the H inbetween the <> which I know is a char. So is there a way to output the char? – boboobobo Dec 05 '15 at 05:47
yep, `cout << nextWord.top()[2] << endl;` – AndersK Dec 05 '15 at 05:48

Dale · Accepted Answer · 2015-12-05T05:57:44.833

1

The problem is this line:

nextWord.push(str[i + 1]);

str[i + 1] is a char, and you're trying to push it onto a string stack. Change it to this, and it should work fine:

nextWord.push(string(1, str[i + 1]));

edited Dec 05 '15 at 05:57

answered Dec 05 '15 at 05:44

Dale

534
4
13

I want to output the H between the <>. So I know right now I need a char or a char* – boboobobo Dec 05 '15 at 05:46
edited answer, see above. Reference: http://stackoverflow.com/questions/17201590/c-convert-from-1-char-to-string – Dale Dec 05 '15 at 05:53

Invalid Conversion from char to string

3 Answers3