substr to char c++ no array
<p>Like the title says I am trying to convert a substr to a char. Ultimately what I am trying to do is tell with a substr is a upper or lowercase letter, I was given the hint that the best way to do that is using the ascii values. This is what I have </p>

<pre><code>for(int i = 0; i&lt;length; i++){
  char a = a.substr(i,1);
 if(a&gt;=65&amp;&amp;a&lt;=90){
   uppercase++;
 }
}
</code></pre>

<p>I get this error here: </p>

<pre><code>string_info.cpp:34:16: error: member reference base type 'char' is not a
      structure or union
     char a = a.substr(i,1);
</code></pre>

<p>I understan that its not working because substr outputs a string and not a char, but what I dont understand is how to get a hold of those ascii values. Does anyone have any ideas?</p>