@end example
@end defun
-@defun substring string start &optional end
+@defun substring string &optional start end
This function returns a new string which consists of those characters
from @var{string} in the range from (and including) the character at the
index @var{start} up to (but excluding) the character at the index
-@var{end}. The first character is at index zero.
+@var{end}. The first character is at index zero. With one argument,
+this function just copies @var{string}.
@example
@group
behaves like @code{string-lessp}.
@end defun
+@defun string-version-lessp string1 string2
+This function compares strings lexicographically, except it treats
+sequences of numerical characters as if they comprised a base-ten
+number, and then compares the numbers. So @samp{foo2.png} is
+``smaller'' than @samp{foo12.png} according to this predicate, even if
+@samp{12} is lexicographically ``smaller'' than @samp{2}.
+@end defun
+
@defun string-prefix-p string1 string2 &optional ignore-case
This function returns non-@code{nil} if @var{string1} is a prefix of
@var{string2}; i.e., if @var{string2} starts with @var{string1}. If