CODEWITHSUNDEEP
c++visual-studio-2012
user2417332
user2417332

Reputation: 59

expression must have pointer type error visual studio 2012

I use visual studio 2012 and when i tried to build this simple program i receive this error and i can't understand where is the problem. Here is my code.

#include "stdafx.h"
#include <iostream>
#include <cmath>
#include <string>
#define MAXN 400 //max digits
using namespace std;

typedef struct {
    //signbit nqma nujda v tozi slu4ai
    char digits[MAXN];
    int lastdigit;
} BigInteger;

BigInteger addBigIntegers(BigInteger *a, BigInteger *b, BigInteger *c)
{
    c->lastdigit = max(a->lastdigit, b->lastdigit);
    int carry = 0;
    for(int i = 0; i<=(c->lastdigit); i++)
    {
        c->digits[i] = (char)(carry + a->digits[i] + b->digits[i]) % 10;
        carry = (carry + a->digits[i] + b->digits[i]) / 10;
    }
    return *c;
}

int main()
{
    BigInteger a;
    BigInteger b;
    string input1;
    string input2;
    cin >> input1 >> input2;
    int len1 = input1.length();
    int len2 = input2.length();
    for(int i = len1-1; i>=0; i--)
    {
         a->digits[i] = 5;
    }
}

The error is on this line:

a->digits[i] = 5;

How can i fix it?

Upvotes: 3

Views: 16955

Answers (2)

Kaathe
Kaathe

Reputation: 335

In C++, object->member is syntactic sugar for (*object).member. That is, it dereferences object before attempting to access member. The dereferencing operator * can only be applied to pointer types.

N.B. There are exceptions to this - if object is an instance of a class which overloads either * or ->, these operators will perform their function as defined in the class. In this case, it is possible to apply these operators to non-pointer objects.

In general, if you want to access a member of a struct or class, use object.member. If you have a pointer to a struct or class, use (*pointer).member, or the shorter pointer->member.

Also, typedef struct is more C than C++. It is more usual to simply declare as struct in C++. So the BigInteger declaration would become:

struct BigInteger {
    char digits[MAXN];
    int lastdigit;
};

A struct in C++ is just a class where all members are public by default.

Upvotes: 5

Michael M.
Michael M.

Reputation: 2584

Short answer : 

a.digits[i] = 5;

Upvotes: 2

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