From: | Neil Conway <neilc(at)samurai(dot)com> |
---|---|
To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
Cc: | PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: int4 <-> bool casts |
Date: | 2005-02-28 00:32:50 |
Message-ID: | 422266B2.6070206@samurai.com |
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Lists: | pgsql-patches |
Peter Eisentraut wrote:
> - Casting back and forth does not preserve information. (This may be
> true for some other type pairs as well, but in this case it's true in
> almost every instance.)
Right, there are many other explicit casts that lose information. In
fact, I think that's somewhat the point of an explicit cast -- if a cast
didn't lose information, it could be done implicitly. By explicitly
casting something, the user is acknowledging that they accept the
possibility of lost information.
> - It's an arbitary definition that is not obviously supported by
> mathematical or similar principles.
It has a long standing precedent outside of mathematics, such as in C
and derived programming languages.
-Neil
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