title: Issue with evaluating ' regexp ' for '\c+' , ' \i\c* ' and ' [\i-[:]][\c-[:]]* '
body: <p>I Am working on a TCL GUI, and I obtain the Data Tree structure for the GUI from a XML Schema, and I have to validate the entry fields fro the restrictions as in the XML Schema. In the XML Schema I am working with I have the simple types NMTOKEN Name and NCName with pattern restrictions '<code>\c+</code>' , '<code>\i\c*</code>' and '<code>[\i-[:]][\c-[:]]*</code>' respectively.
  The code i use to check is </p>
  
  <pre><code>method validatePatternValue { value } { 
      set patternCheck 1
  
      set pattern "^($patternValue)\$"
      set patternCheck [regexp $pattern $value]
  
      if {$patternCheck == 0} {
          tk_messageBox -message "Only Characters within range $patternValue for $patternValueType is\
                                  accepted "
          return 0
      } 
  
      return 1
  }
  </code></pre>
  
  <p>and whenever the $pattern is one of these '<code>\c+</code>' , '<code>\i\c*</code>' and '<code>[\i-[:]][\c-[:]]*</code>' my text field does not accept any input and keeps throwing an error exception dialogue.</p>
  
  <p>Just to add some more info, I came across this website, with some good info regarding my question about processing combinations of '<code>\i</code>' and '<code>\c</code>'. But is there no other way apart from the one suggested in the following link : <a href="http://www.regular-expressions.info/xmlcharclass.html" rel="nofollow">XML Schema Character Classes</a></p>