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To: Itai Zukerman <zukerman@math-hat.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Polymorphic? 
In-reply-to: <87lm041jnq.fsf@matt.w80.math-hat.com> 
References: <87lm041jnq.fsf@matt.w80.math-hat.com>
Comments: In-reply-to Itai Zukerman <zukerman@math-hat.com>
	message dated "Tue, 25 Feb 2003 10:09:45 -0500"
Date: Tue, 25 Feb 2003 11:20:11 -0500
Message-ID: <10960.1046190011@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Itai Zukerman <zukerman@math-hat.com> writes:
> I'd like to define a C function that takes two arguments of type
> "array of <fixed-length type>" and returns an INT4.  The function
> would make use of the <, <=, =, >=, > operators on the base type.  Any
> examples of or documentation on how to:

> 1.  Extract information about the underlying type from the arrays, in
>     particular the size of the type?
> 2.  Apply an operator from within C?

contrib/array might be a useful example of array manipulation.  As for
the other stuff, do you actually want to invoke those operators
specifically, or are you looking for sorting?  In any case you might
prefer to use any_ordering_op, SelectSortFunction and ApplySortFunction
rather than nailing down your own assumptions about what to compare
with.

			regards, tom lane