Fix buggy less function.

Allowing rankings among types which documentation says
are not comparable.

* lib.c (enum less_handling): New enum.
(less_tab): Elements are values of the less_handling enum.
(less_tab_init): Entries are renumbered.  Everything that was
given precedence 5 or higher is now zero: not comparable.
Precedences 0 to 4 remap to 1 to 5. less_tab is populated
differently, since there are four values now. If either
the left or right type has 0 precedence, the value is
less_cannot: comparison is not possible.
(less): Only a less_tab value of less_compare now passes
control through to the switch statement. The less_cannot
value shortcuts to a cannot compare error.
Types that cannot occur in the switch now are removed,
and a default case goes to internal error.

0 files changed, 0 insertions, 0 deletions