title: Check if string has letter in uppercase or lowercase
body: <p>i would like to know if it's possible check if one letter of a string is capitalized. Other way to see it, if all letters in the string are uppercase or lowercase.  Example:</p>
  
  <pre><code>string a = "aaaaAaa"; 
  string b = "AAAAAa"; 
  
  if(??){ //Cheking if all the string is lowercase
     cout &lt;&lt; "The string a contain a uppercase letter" &lt;&lt; endl;
  }
  if(??){ //Checking if all the string is uppercase
         cout &lt;&lt; "The string b contain a lowercase letter" &lt;&lt; endl;
  }
  </code></pre>