title: expression must have pointer type error visual studio 2012
body: <p>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.</p>
  
  <pre><code>#include "stdafx.h"
  #include &lt;iostream&gt;
  #include &lt;cmath&gt;
  #include &lt;string&gt;
  #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-&gt;lastdigit = max(a-&gt;lastdigit, b-&gt;lastdigit);
      int carry = 0;
      for(int i = 0; i&lt;=(c-&gt;lastdigit); i++)
      {
          c-&gt;digits[i] = (char)(carry + a-&gt;digits[i] + b-&gt;digits[i]) % 10;
          carry = (carry + a-&gt;digits[i] + b-&gt;digits[i]) / 10;
      }
      return *c;
  }
  
  int main()
  {
      BigInteger a;
      BigInteger b;
      string input1;
      string input2;
      cin &gt;&gt; input1 &gt;&gt; input2;
      int len1 = input1.length();
      int len2 = input2.length();
      for(int i = len1-1; i&gt;=0; i--)
      {
           a-&gt;digits[i] = 5;
      }
  }
  </code></pre>
  
  <p>The error is on this line:</p>
  
  <pre><code>a-&gt;digits[i] = 5;
  </code></pre>
  
  <p>How can i fix it?</p>