Proposal: add full complement of support for decreasing things in Data.Map

wren romano winterkoninkje at
Fri May 20 05:00:49 UTC 2016

On Thu, May 19, 2016 at 10:00 AM, David Feuer <david.feuer at> wrote:
> Data.Map offers functions to convert from ascending lists to maps, and also
> offers a function to map an increasing function over the keys of a map.
> Equivalents for descending lists and decreasing functions are missing. I
> think we should add them. Any objections?


They're a lot more performant to do directly rather than (a) reversing
the ascending lists, or (b) constructing the mirror image (Map (Down
k) a) so that "ascending" is in the right order.

Live well,

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