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Re: binary operators on integers

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Marko Kreen <marko(at)l-t(dot)ee>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: binary operators on integers
Date: 2000-10-24 20:23:55
Message-ID: Pine.LNX.4.21.0010242219020.1165-100000@peter.localdomain (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
This patch was installed, with xor as "#".  The parser still needs work.  
Besides the known issue of "|", this also parses funny:

=> select 5 & ~ 6;
ERROR:  Unable to identify a right operator '&' for type 'int4'


Marko Kreen writes:

> Here is my next take on binary operators for integers.
> It implements the following operators for int2/int4/int8:
> 
>  ~ - not
>  & - and
>  ^ - xor
>  | - or
>  << - shift left
>  >> - shift right
> 
> Notes:
> 
> * My original choice for xor was '#' because the '^' operator conflicts
>   with power operator on floats but Tom Lane said:
> 
> > Well, you *could* use '^' since there's no definition of it for integer
> > operands.  But that would mean that something like '4^2', which was
> > formerly implicitly coerced to float and interpreted as floating
> > power function, would suddenly mean something different.  Again a
> > serious risk of silently breaking applications.  This doesn't apply to
> > '|' though, since it has no numeric interpretation at all right now.
> 
>   As the bit-string uses '^' too for xor-ing it would be nice to be
>   consistent.  I am quite unsure on this matter.  The patch now seems
>   otherwise sane to me, this is the only issue left.
> 
> * On << and >> the second argument is always int32 as this seems
>   to be the 'default' int type in PostgreSQL.
> 
> * Oids used are 1874 - 1909.
> 
> Comments?
> 
> Patch is against current CVS.
> 
> 

-- 
Peter Eisentraut      peter_e(at)gmx(dot)net       http://yi.org/peter-e/


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