| From: | John R Pierce <pierce(at)hogranch(dot)com> |
|---|---|
| To: | Howard Rogers <hjr(at)diznix(dot)com> |
| Cc: | Stephen Cook <sclists(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Bitmask trickiness |
| Date: | 2010-07-23 16:52:22 |
| Message-ID: | 4C49C8C6.5040803@hogranch.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
the universal solution is a AND with one mask (which has a 1 in every
position you wish to test for and a zero in each position you wish to
ignore) and an XOR with another mask (that has a 1 in each position that
you want to test for a 1 and a zero in each position that you wish to
test for a 0)), then a test if the result is == zero.
in a language like SQL, this could be simplified to a AND with MASK1 and
a COMPARE for equality with MASK2, with the same result.
-jrp
(old assembler programmer)
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