title: What is "error : invalid use of void expression"?
body: <p>I am trying to create a hexadecimal to base64 converter. I don't know if I am going in the right direction converting binary as I am attempting to do now or if there is a more direct way of converting. Any suggestions on the math of converting or how to code hex to base64 would be very helpful.</p>
  
  <p>On the contrary, I have been receiving the error(The new one since updated code):</p>
  
  <pre><code>hexto64.c: In function ‘main’:
  hexto64.c:21:17: error: lvalue required as left operand of assignment
  ReVerse(input) = RevHex;
                 ^
  </code></pre>
  
  <p>If anybody could help explain what this error means and how to fix
  would help greatly! Thank you in advance.</p>
  
  <p>EDIT: So thanks to the few people in the comments, I now understand the error.</p>
  
  <p>Here is my code(Updated):    </p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;math.h&gt;
  #include &lt;string.h&gt;
  
  char ReVerse(const char *str)
  {
      if (*str != '\0')
              ReVerse((str + 1));
      printf("%c", *str);
  }
  
  
  
  int main()
  {
      char RevHex;
      char input[4096] = {0};
  
      printf("Enter Hexadecimal: ");
      scanf("%s", input);
      RevHex = ReVerse(input);
      printf("\n");
      return 0;
  }
  </code></pre>
  
  <p>Last edit: I have found the error in my code. Thank you guys for all the feedback!</p>