Inaccuracy in Emacs manual.

[Luc Teirlinck]

Do C-h m emacs m indentation m just spaces.  We see:

    There are also commands to convert tabs to spaces or vice versa,
    always preserving the columns of all nonblank text.  `M-x tabify'
    scans the region for sequences of spaces, and converts sequences
    of at least three spaces to tabs if that can be done without
    changing indentation.  `M-x untabify' changes all tabs in the
    region to appropriate numbers of spaces.

M-x tabify actually converts sequences of at least two (not three as
erroneously mentioned above) spaces to tabs.  As another current
thread shows, this is not meaningless nitpicking.

Paste the following into the scratch buffer:

(setq aaaa '(?  ?a))

Just two spaces after the ?  .  Put the region around the expression
and do M-x tabify.  The two spaces are now a tab, changing the car of
the list from space to tab.

'(? ?a) is safe.

Sincerely,

Luc.