Re: COMMUTATOR doesn't seem to work

On 12-06-22 07:11 AM, Florian Pflug wrote:
> On Jun22, 2012, at 06:32 , D'Arcy Cain wrote:
>> So I have my type working now but I had to create a new C function
>> that take the opposite argument order. Seems redundant but I could
>> not see a better way.
>
> There isn't. Postgres itself contains a huge number of such functions,
> e.g. for every *lt() (less-than) there's a *gt() (greater-than).

Right but that's not the same thing. Assuming you meant lt/gte and
lte/gt those still are not self-commutating (SC). For example, '='
on two ints is SC. The issue here is that the operator is SC but
the args are different types. It would be nice if there was a way
to automatically generate code that reverses arguments. Maybe such
a thing belongs in the CREATE FUNCTION command.

Or, I guess this works and keeps from creating a second C function:

CREATE OR REPLACE FUNCTION eq(chkpass, text)
RETURNS bool
STRICT
AS 'chkpass.so', 'chkpass_eq'
LANGUAGE 'c'
RETURNS NULL ON NULL INPUT;

CREATE OR REPLACE FUNCTION eq(text, chkpass)
RETURNS bool
AS 'select eq($2, $1);'
LANGUAGE SQL
RETURNS NULL ON NULL INPUT;

--
D'Arcy J.M. Cain <darcy(at)druid(dot)net> | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
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