title: C++ undefined reference to defined function
body: <p>I cannot figure out why this is not working.  I will put up all three of my files and possibly someone can tell me why it is throwing this error.  I am using g++ to compile the program.</p>
  
  <p>Program:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include "h8.h"
  
  using namespace std;
  
  int main()
  {
    char sentence[MAX_SENTENCE_LENGTH];
    char writeTo[] = "output.txt";
    int distanceTo,likePosition, length, numWords;
    cout &lt;&lt; "ENTER A SENTENCE!   ";
    cin.getline(sentence, 299);
    length = strlen(sentence);
    numWords = wordCount(sentence, length);
    for(int x = 0; x &lt; 3; ++x)
    {
      likePosition = likePos(numWords);
      distanceTo = lengthTo(sentence, likePosition, length);
      insertLike(sentence, distanceTo, length, writeTo);
    }
    return 0;  
  }
  </code></pre>
  
  <p>Function file:</p>
  
  <pre><code>void insertLike(const char sentence[],  const int lengthTo, const int length, char writeTo[])
  {
    char part1[MAX_SENTENCE_LENGTH], part2[MAX_SENTENCE_LENGTH];
    char like[] = " like ";
    for(int y = 0; y &lt; lengthTo; ++y)
      part1[y] = sentence[y];
    for(int z = lengthTo+1; z &lt; length - lengthTo; ++z)
      part2[z] = sentence[z];
    strcat(part1, like);
    strcat(part1, part2);
    writeToFile(sentence, writeTo);
    return;
  }
  </code></pre>
  
  <p>Header file:</p>
  
  <pre><code>void insertLike(const char sentence[], const int lengthTo, const int length, const char writeTo[]);
  </code></pre>
  
  <p>The error exactly is:</p>
  
  <pre><code>undefined reference to 'insertLike(char const*, int, int, char const*)'
  collect2: ld returned 1 exit status
  </code></pre>