The @code{concat} function always constructs a new string that is
not @code{eq} to any existing string.
-When an argument is an integer (not a sequence of integers), it is
-converted to a string of digits making up the decimal printed
-representation of the integer. @strong{Don't use this feature; we plan
-to eliminate it. If you already use this feature, change your programs
-now!} The proper way to convert an integer to its decimal printed form
-is with @code{format} (@pxref{Formatting Strings}) or
+In Emacs versions before 21, when an argument was an integer (not a
+sequence of integers), it was converted to a string of digits making up
+the decimal printed representation of the integer. This obsolete usage
+no longer works. The proper way to convert an integer to its decimal
+printed form is with @code{format} (@pxref{Formatting Strings}) or
@code{number-to-string} (@pxref{String Conversion}).
-@example
-@group
-(concat 137)
- @result{} "137"
-(concat 54 321)
- @result{} "54321"
-@end group
-@end example
-
For information about other concatenation functions, see the
description of @code{mapconcat} in @ref{Mapping Functions},
@code{vconcat} in @ref{Vectors}, and @code{append} in @ref{Building