Re: Range Types - typo + NULL string constructor

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Florian Pflug <fgp(at)phlo(dot)org>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Erik Rijkers <er(at)xs4all(dot)nl>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Range Types - typo + NULL string constructor
Date: 2011-09-22 06:01:22
Message-ID: 1316671282.7281.228.camel@jdavis
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On Thu, 2011-09-22 at 02:31 +0200, Florian Pflug wrote:
> My personal favourite would be '0', since it resembles the symbol used
> for empty sets in mathematics, and we already decided to use mathematical
> notation for ranges.
>
> If we're concerned that most of our users won't get that, then 'empty'
> would be a viable alternative I think.
>
> From a consistency POV it'd make sense to use a bracket-based syntax
> also for empty ranges. But the only available options would be '()' and '[]',
> which are too easily confused with '(,)' and '[,]' (which we already
> decided should represent the full range).

Yes, I think () is too close to (,).

Brainstorming so far:
0 : simple, looks like the empty set symbol
empty : simple
<empty> : a little more obvious that it's special
<> : visually looks empty
- : also looks empty
{} : mathematical notation, but doesn't quite fit ranges

I don't have a strong opinion. I'd be OK with any of those.

Regards,
Jeff Davis

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