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Re: int4 <-> bool casts

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
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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.


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