Extension to scanString, to modify matching text with modified tokens that may
   be returned from a parse action.  To use transformString, define a grammar and
   attach a parse action to it that modifies the returned token list.
   Invoking transformString() on a target string will then scan for matches,
   and replace the matched text patterns according to the logic in the parse
   action.  transformString() returns the resulting transformed string.

01103                                          :
        """Extension to scanString, to modify matching text with modified tokens that may
           be returned from a parse action.  To use transformString, define a grammar and
           attach a parse action to it that modifies the returned token list.
           Invoking transformString() on a target string will then scan for matches,
           and replace the matched text patterns according to the logic in the parse
           action.  transformString() returns the resulting transformed string."""
        out = []
        lastE = 0
        # force preservation of <TAB>s, to minimize unwanted transformation of string, and to
        # keep string locs straight between transformString and scanString
        self.keepTabs = True
        for t,s,e in self.scanString( instring ):
            out.append( instring[lastE:s] )
            if t:
                if isinstance(t,ParseResults):
                    out += t.asList()
                elif isinstance(t,list):
                    out += t
                else:
                    out.append(t)
            lastE = e
        out.append(instring[lastE:])
        return "".join(map(_ustr,out))