invalid conversion from 'int' to 'const char*'

Question

I'm using gcc on codeblocks and I'd like to write a function that uses an array of records.

However I keep getting the error:

invalid conversion from 'int' to 'const char*'

The code:

#include <iostream>
#include <string>

using namespace std;

struct rendeles {
    string nev;
int mennyiseg;
};

struct teaceg {
string nev;
int mennyiseg;
};

int szam; 
struct rendeles rendelt [100];      
struct teaceg cegek [100];          
int h;

int hanyadikceg (string cegnev)
{                            
    for (int i=0;i<szam;i++)
    {
        if (cegek[i].nev==cegnev)
            {
                return i;
            }
    }
    return -1;
}

int main()
{
    cout << "Hány db rendelés lesz összesen?";
    cin >> szam;
    if (szam > 100)
    {
        cout << "Hiba: túl nagy a rendelések száma! (100 a maximum)";
        return -1;
    }

    for (int i=0;i<szam;i++)        
    {
        cout << "A(z) " << i+1 <<". cég neve:";
        cin >> rendelt[i].nev;                                 
        cout << "A(z) " << i+1 <<". rendelés mennyisége:";
        cin >> rendelt[i].mennyiseg;                           
    }
    cout << endl;

    h = hanyadikceg('Lipton');              //the problem is in this line
    cout << "Hanyadik cég a xyz:" << h;

    for (int i=0;i<szam;i++)          
    {
        cout << "A(z) " << i+1 << ". rendelés: " << rendelt[i].nev << " " <<     rendelt[i].mennyiseg << endl;
    }

    return 0;
}

What causes this error?

btw: having function and variable names in the lingua franca of programming makes it far easier to get help, since far more people are able to understand the code. — PlasmaHH, Mar 14 '12 at 13:05
@Jesse: google translate autodetection claims it is hungarian. — PlasmaHH, Mar 14 '12 at 13:11
Yes, it's Hungarian. I wrote it in this language, because it was a school assignment, and we used all variables in Hungarian. But I know it's better to use English for most purposes. Btw, I don't know how this became a "famous question"? — GregT, Sep 04 '16 at 20:09

score 20 · Accepted Answer · answered Mar 14 '12 at 13:04

20

You need to use double-quotes (") for string literals, not single-quotes (').

answered Mar 14 '12 at 13:04

Oliver Charlesworth

267,707
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score 4 · Answer 2 · answered Mar 14 '12 at 13:05

4

You are using single quotes ('Lipton'). Single quotes are for char-literals.

Use "Lipton", for a const char* literal.

answered Mar 14 '12 at 13:05

Moo-Juice

38,257
10
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128

George Skoptsov · Answer 3 · 2012-03-14T13:11:47.427

4

Change 'Lipton' to "Lipton" in the problem line and the compilation error will go away.

In C/C++, double-quoted expressions are strings (or, technically, string literals) and resolve to char * or const char * type, while single-quoted expressions are characters (or character literals) and resolve to char type (which can be implicitly casted to int). That explains your error: the compiler cannot convert the char integer type to the const char * that the function signature requires.

edited Mar 14 '12 at 13:11

answered Mar 14 '12 at 13:06

George Skoptsov

3,831
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Just a note. String literals are *always* resolved to `const`. – Moo-Juice Mar 14 '12 at 13:58
1

String literals in C++ have type `const char[N]`, where N is the length of the string including nul terminator. There's an implicit conversion to `const char*`, and in C++03 there's a deprecated conversion to `char*` for compatibility with C. IIRC, the deprecated conversion is removed in C++11. The function `hanyadikceg` calls for a `std::string`, and there's another implicit conversion from `const char*` to `std::string`. – Steve Jessop Mar 14 '12 at 14:05

score 2 · Answer 4 · answered Mar 14 '12 at 13:06

2

h = hanyadikceg('Lipton');

should be

h = hanyadikceg("Lipton");

answered Mar 14 '12 at 13:06

Lou

1,955
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16

invalid conversion from 'int' to 'const char*'

4 Answers4

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