> On Apr 6, 2020, at 19:44 , David G. Johnston <david.g.johns...@gmail.com> 
> wrote:
> 
> On Mon, Apr 6, 2020 at 6:12 PM Guyren Howe <guy...@gmail.com 
> <mailto:guy...@gmail.com>> wrote:
> Consider this:
> 
> select (array[array[1, 2], array[3, 4]])[i:i]
> from generate_subscripts(array[array[1, 2], array[3, 4]], 1) i
> 
> which produces:
> 
> {{1,2}}
> {{3,4}}
> 
> I expect and want, from that source:
> 
> {1, 2}
> {3, 4}
> 
> 
> Also: could we _please_ get a version of unnest that doesn’t explode any 
> number of dimensions into 1?

Here’s a solution in pure SQL, for reference:

CREATE OR REPLACE FUNCTION public.pairwise(
    cards card[]
)
RETURNS table(c1 card, c2 card)
        LANGUAGE sql
AS $function$
with
individual_cards as (
    select
        *
    from 
        unnest(cards) with ordinality c
)

select
    c(c1.suit, c1.rank),
    c(c2.suit, c2.rank)
from 
    individual_cards c1 join
    individual_cards c2 on c1.ordinality = c2.ordinality - 1
where 
    c1.ordinality % 2 = 1
    
$function$
;

Given that Postgres often (with good cause) touts its type system, it’s a shame 
that this basic structured type is great in many ways, but seriously flawed in 
really simple ones.

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