On Jan5, 2011, at 10:25 , Peter Eisentraut wrote: > On sön, 2011-01-02 at 12:47 +0100, Florian Pflug wrote: >> The only way around that would be to introduce magic constants "lower", >> "upper" that >> can be used within index expressions and evaluate to the indexed dimension's >> lower >> and upper bound. You'd then use >> >> my_array[upper], my_array[upper-1], ... >> >> to refer to the last, second-to-last, ... element in the array. Actually >> doing this >> could get pretty messy, though - not sure if it's really worth the effort... > > How about just some functions: > > array_first(array, dim) > array_last(array, dim)
You image these to return the actual element, not the first and last index value, right? Because we already have array_lower() and array_upper() which return the lower and upper index bound for a certain dimension. (http://www.postgresql.org/docs/9.0/interactive/functions-array.htm) A more general solution would be a function array_relative(array anyarray, indices int[]) which would return the element indexed by <indices>, where positive indices are assumed to be relative to the respective dimension's lower bound and negative indices to the upper bound + 1. For slices, we could additionally have array_relative(array anyarray, indices_start int[], indices_end int[]) best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
