Re: Array behavior oddities

Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> >   If any dimension is written as a slice, i.e. contains a colon, then all
> >   dimensions are treated as slices.
> 
> > Is the the behavior of assuming an entry with no colon is a slice what
> > we want, or are we just stuck with it?
> 
> Why do you find that surprising?  It's either a slice or it isn't,
> there's no halfway point.  Are you proposing to throw an error if only
> some of the subscripts have colons?  What would be the point?

What is confusing is if I see [1:3][2], I assume that is [1:3][2:2], not[1:3][1:2].  By what logic does [2] mean from 1
to2?
 

For example, in [1:3][2], [2] means [1:2], two elements, but in [1][2],[2] means one element.

> > Is there a reason out-of-bounds array accesses behave differently for
> > slices and non-slices?
> 
> History (although "sloppy original implementation" would do too).  I'm
> not sure if we should try to clean it up --- there've not been that many
> complaints, but I'm sure we'd get complaints from people whose code
> stopped working, if we change it.

OK, so there is no grand design I am missing;  it is just a wart in our
implementation, that at least we document.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://postgres.enterprisedb.com
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