Generate the directory stack aliases with a loop.

directory.zsh

@@ -10,13 +10,9 @@ setopt EXTENDED_GLOB        # Use extended globbing syntax.
 unsetopt CLOBBER            # Don't overwrite existing files with > and >>.
                             # Use >! and >>! to bypass.
 
-alias 1='cd -'
-alias 2='cd +2'
-alias 3='cd +3'
-alias 4='cd +4'
-alias 5='cd +5'
-alias 6='cd +6'
-alias 7='cd +7'
-alias 8='cd +8'
-alias 9='cd +9'
+# Aliases
+for index in {1..9}; do
+  alias "$index"="cd +${index}"
+done
+unset index