title: Verify that string contains only letters
body: <p>I have an input field which should accept only letters (doesn't matter lower or uppercase).
  I could write this simply by using co ca (contains only/any) operator. But it's time consuming.</p>
  
  <pre><code>  if p_input3 ca '*/ + - ? ! % ( ) = 0123456789'.
      MESSAGE e000 WITH 'Only letters are allowed. No numbers or special characters'.
    ENDIF.
  </code></pre>
  
  <p>It works. But I wanted to check it using regex.
  I tried this code. But It doesn't work quite well.</p>
  
  <pre><code>DATA: text TYPE string,
        matcher type REF TO cl_abap_matcher.
  
  PARAMETERS: p_input3 TYPE string DEFAULT 'abCD*()fhi' LOWER CASE.
  
  matcher = cl_abap_matcher=&gt;create(
     pattern = `([a-zA-Z])`
      text = p_input3
    ).
  
    if matcher = abap_true.
      MESSAGE e000 with 'Only letters are allowed. No numbers or special characters'.
    ENDIF.
  </code></pre>
  
  <p>Could anyone figure it out?</p>