@cindex replace characters
This function replaces all occurrences of the character @var{old-char}
with the character @var{new-char} in the region of the current buffer
-defined by @var{start} and @var{end}.
+defined by @var{start} and @var{end}. Both characters must have the
+same length of their multibyte form.
@cindex undo avoidance
If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does
@defun subst-char-in-string fromchar tochar string &optional inplace
@cindex replace characters in string
This function replaces all occurences of the character @var{fromchar}
-with @var{tochar} in @var{string}. Unless @var{inplace} is non-nil,
-substitution occurs in a copy of @var{string}. In any case, the
-function returns the resulting string. Both characters must have the
-same multi-byte length.
+with @var{tochar} in @var{string}. By default, substitution occurs in
+a copy of @var{string}, but if the optional argument @var{inplace} is
+non-@code{nil}, the function modifies the @var{string} itself. In any
+case, the function returns the resulting string.
@end defun
@deffn Command translate-region start end table