remove first character from line

How would I remove the first character from each line of a file?
I put each line into temp and try to change the first character but it tells me that I can't convert from "const char" to "char".

Code:

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#include <iostream>
#include <fstream>

using namespace std;

int main(void)
{
    ifstream file;
    ofstream out;

    file.open("first.txt");
    out.open("temp.txt");

    string temp;

    while(file.good())
    {
        getline(file, temp);

        temp[0] = ""; //doesn't work
        out << temp << endl;
    }

    out.close();
    file.close();

    cin.get();
    return 0;
}

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Use the string::erase() member function.

thanks.

it seems to work now after changing

Code:

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temp = "";

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to

Code:

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temp.erase(0,1);

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Code:

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temp[0] = '\0';

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This will produce no syntax errors.

Anything contained within "quotes" can be considered as a char* pointer, even if there's a single character in it. So, by putting temp[0] = ""; you basically tried to assign a char* pointer to something that expected a character.

You should use the functions already described to you, if they do the trick, but I believe it's even more important to understand why the compiler is complaining.

Try this code for an example:
cout << (int) "a" << endl;
cout << (int) 'a' << endl;
cout << (int) "" << endl;
cout << (int) '\0' << endl;

Quote:

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Originally Posted by Mr.Pointer

Code:

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temp[0] = '\0';

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This will produce no syntax errors.

Anything contained within "quotes" can be considered as a char* pointer, even if there's a single character in it. So, by putting temp[0] = ""; you basically tried to assign a char* pointer to something that expected a character.

You should use the functions already described to you, if they do the trick, but I believe it's even more important to understand why the compiler is complaining.

Try this code for an example:
cout << (int) "a" << endl;
cout << (int) 'a' << endl;
cout << (int) "" << endl;
cout << (int) '\0' << endl;

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will these actually work in C++? i thought (int) var stuff belongs to C! and type casting in C++ differs actually!

Code:

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static_cast<int> (sth)

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i'd be very thankful if you or anyone else can make it clearer .

Quote:

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Originally Posted by Mr.Pointer

This will produce no syntax errors.

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It will also do the wrong thing since temp is a std::string object. Actually, even if temp was a null terminated string, assigning a null character to the first character will just truncate the string to zero length instead of removing the first character. The solution that not_someguy eventually used is correct.

Quote:

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Originally Posted by Mr.Pointer

Anything contained within "quotes" can be considered as a char* pointer, even if there's a single character in it. So, by putting temp[0] = ""; you basically tried to assign a char* pointer to something that expected a character.

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Loosely speaking, that is true, but technically "" is a const char[1], not a char*.

Quote:

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Originally Posted by Masterx

will these actually work in C++? i thought (int) var stuff belongs to C! and type casting in C++ differs actually!

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I recommend the use of the appropriate cast like static_cast in C++, but otherwise the C-style casts still work in C++.

Quote:

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It will also do the wrong thing since temp is a std::string object

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Yeah, like I said, he should use the functions suggested to him. I just thought it would be very important to understand just why it produced a syntax error.

Quote:

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Loosely speaking, that is true, but technically "" is a const char[1], not a char*.

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Not that it changes anything in the long run, but thanks for the clarification :)

Quote:

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I recommend the use of the appropriate cast like static_cast in C++, but otherwise the C-style casts still work in C++.

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I only recently migrated to C++ after having a basic knowledge of C, and I'm still using C-style casting. Thank you for your suggestion, I will look into it.