title: How to check if all letters in UTF-8 string are ASCII?
body: <p>How to check that all string characters are ASCII? It is sad in <a href="http://wiki.freepascal.org/LCL_Unicode_Support" rel="nofollow">documentation</a>:</p>
  
  <blockquote>
    <p>Unicode characters U+0000 to U+007F (ASCII) are encoded simply as
    bytes 00h to 7Fh (ASCII compatibility). This means that files and
    strings which contain only 7-bit ASCII characters have the same
    encoding under both ASCII and UTF-8. All characters >U+007F are
    encoded as a sequence of several bytes, each of which has the two most
    significant bits set.</p>
  </blockquote>
  
  <p>So I wonder how to check string to be ASCII?</p>