strepex

             Performs replacements of parts in strings by using
             regular expressions (REPlacement of regular
             EXpressions). Subexpressions may be also
             inserted into the replacement string.

             String processing

             newstring = strepex( string, expression, [replacement],
                                 /fold_case, /all)

             string     -  the string which will be analyzed and whose
                           parts will be replaced in return.
             expression -  A regular expression as being used for the
                           REGEX function. Subexpressions must be
                           given in parentheses.
             replacement - String to replace for matching regular
                           expressions. If it contains "&n" it
                           will be replaced with the n-th
                           subexpression in expression above
                           (starting from 0). "&" may be escaped with
                           "\&", "\" with "\\".
                           If not given replacement will be empty
                           string (deletion of string).

              fold_case -  Use case-insensitive regular expression
                           matching. But replacement remains case
                           sensitive.
              all      -   Replace all occurrences of expression in
                           given string. Default is to replace only
                           the first occurrence of expression.

              Returns the input string with a replacement of all
              occurrences of a matching expression by the replacement
              (which in turn may contain replacements of
              subexpressions).
              If no subexpression was found the input string remains
              unaltered.

            Do not use in time critical sections: It involves lot of
            looping on  input and replacement string (but the
            recursion mentioned in earlier versions was replaced to
            allow escaping).

             s = "x5*y3+2"
             s1 = strepex(s,"(x|y)([0-9])","&0(&1)",/all)
             -> s1 contains "x(5)*y(3)+2"

            $Log: strepex.pro,v $
            Revision 1.5  2004/06/30 07:15:46  goehler
            replace of subexpression expansion (&n -> n-th subexpression) with a more
            elaborated but quirky version which now supports escaping within replacement string.
            Revision 1.4  2004/06/29 07:55:01  goehler
            added: internal noexpand keyword which fastens up the subexpression expansion
            waiver: implementation of escaping using "\" is wrong. must be replaced with something else
            Revision 1.3  2003/04/09 13:03:37  goehler
            updated documentation/fix of example bug
            Revision 1.2  2002/09/10 07:01:51  goehler
            typos/fixed aitlib html style
            Revision 1.1  2002/09/04 14:59:26  goehler
            string function to perform regular expression replacements.

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