@code{(require 'chapter-order)} @ftindex chapter-order The @samp{chap:} functions deal with strings which are ordered like chapter numbers (or letters) in a book. Each section of the string consists of consecutive numeric or consecutive aphabetic characters of like case. @defun chap:string? string1 string2 @defunx chap:string<=? string1 string2 @defunx chap:string>=? string1 string2 Implement the corresponding chapter-order predicates. @end defun @defun chap:next-string string Returns the next string in the @emph{chapter order}. If @var{string} has no alphabetic or numeric characters, @code{(string-append @var{string} "0")} is returnd. The argument to chap:next-string will always be @code{chap:string