Compiler error: invalid conversion from 'int' to 'int*' [-fpermissive]|

问题

I got a compiler error:

main.cpp|59|error: invalid conversion from 'int' to 'int*' [-fpermissive]|

The offending line is

int *pComienzo = vector, *pFinal = vector[nElementos-1];

Why there is an error? Can someone help me?

Below is my code:

#include <iostream>
#include <ctype.h>

using namespace std;
const unsigned short int MAX_VAL = 10;

int LongitudCadena(char*);

int BuscarCaracter(char *cadena, char caracter);

void Ordenar(int *vector, int nElementos, bool ascendente);

int main()
{
    char *cadena = "asdasd";

    cout << LongitudCadena(cadena) << endl;

    cout << BuscarCaracter(cadena, 'a') << endl;

    int iArray[] = {5,4,3,2,1};

    Ordenar(iArray, 5, 1);

    cout << iArray << endl;

    return 0;
}

int LongitudCadena(char *cadena)
{
    char *c = cadena;
    for(int i = 0; i < MAX_VAL; i++)
    {
        if (c[i] == 0) break;
        cadena++;
    }

    return  cadena - c;
}

int BuscarCaracter(char * cadena, char caracter)
{
    char *pCadena = cadena;
    for (int i = 0; i < MAX_VAL; i++)
    {
        pCadena++;
        if (toupper(cadena[i]) == toupper(caracter))
        return pCadena- cadena;
    }

    return -1;
}

void Ordenar(int *vector, int nElementos, bool ascendente)
{


    int *pComienzo = vector, *pFinal = vector[nElementos-1];

    if (ascendente)
    {
        for (int i = 0; i < nElementos; i++)
        {
            for (; pComienzo < pFinal; pComienzo++, pFinal--)
            {
                if (*pComienzo > *pFinal)
                {
                    *pComienzo += *pFinal;
                    *pFinal -= *pComienzo;
                    *pComienzo -= *pFinal;
                }
            }
        }
    }
}

I'm learning...

回答1:

Your error is in this line:

int *pComienzo = vector, *pFinal = vector[nElementos-1];

The reason for this is that vector is an int*, but vector[nElementos - 1] is a regular int. Thus the declaration

int *pFinal = vector[nElementos - 1];

is trying to assign the integer value at the last index of vector to the pointer pFinal, hence the compiler error.

To fix this, you may want to do either

int *pFinal = &vector[nElementos - 1];

which makes pFinal point to the last element of vector, or

int *pFinal = vector + (nElementos - 1);

which accomplishes the same thing using pointer arithmetic.

That said, since you're working in C++, why not use the provided std::vector type and avoid working with pointers altogether?

Hope this helps!

回答2:

vector is a pointer, but subscripting it as vector[nElementos-1] dereferences it to simply an int. What it looks like you want is instead

int *pComienzo = vector, *pFinal = &(vector[nElementos-1]);

回答3:

An array access/subscript (i.e., a[i] where a is an array/pointer and i is an integer) is an expression with the type being the thing you have in the array.

Simply use the address-of operator & to store the address in the pointer:

int *pComienzo = vector, *pFinal = &vector[nElementos-1];

回答4:

You forgot &. vector[nElementos-1] is the value, while you need an address for pFinal.

Either *pFinal = &(vector[nElementos-1]) or *pFinal = vector + nElementos-1.

来源：https://stackoverflow.com/questions/9167834/compiler-error-invalid-conversion-from-int-to-int-fpermissive

标签

c++

arrays

pointers