test=# create or replace function sys_catalog.bool_eq_numeric(bool, numeric) returns bool as $$ select $1::numeric = $2; $$ language sql;

CREATE FUNCTION

test=# create operator sys_catalog.= (procedure = bool_eq_numeric,leftarg = bool,rightarg = numeric,commutator = =);

CREATE OPERATOR

test=#

test=# create or replace function sys_catalog.numeric_eq_bool(numeric, bool) returns bool as $$ select $1 = $2::numeric; $$ language sql;

CREATE FUNCTION

test=# create operator sys_catalog.= (procedure = numeric_eq_bool,leftarg = numeric,rightarg = bool,commutator = =);

CREATE OPERATOR

test=# select 1::numeric=1::int;

ERROR:  operator is not unique: numeric = integer

LINE 1: select 1::numeric=1::int;

                         ^

HINT:  Could not choose a best candidate operator. You might need to add explicit type casts.