In working through a recent project, I realized that Clojure has a
nice collection of functions for working with maps. However, it
doesn't seem to have analogues of some of the important sequence tools
(filter and map most noticeably, probably others).
Given that map will take a map as a collection argument - generating a
sequence of entries - it isn't hard to write those analogues. Turning
them back into maps is sort of ugly, because there doesn't seem to be
a natural way to turn a sequence of entries into a map (someone
correct me?), but still not hard.
There are some issues with doing this in general - do you use keys,
values or entries from the map? If you're modifying instead of
filtering, do you modify the key, value or entry? Rolling your own,
you can decide what you need when you write it, but trying to
generalize them all might get ugly.
The nasty part of all this is that I seem to have to specify the
resulting map type in the function that turns the sequence of entries
back into keys. I.e. - if I want to run the same filter over both a
hash-map and a sorted-map and need to preserve the sortedness, I
either need two map filter functions, or have to turn the hash-map
into a sorted-map after filtering it.
Hmm - there doesn't even seem to be an easy way to convert between the
two map types.
So, the questions: what have I missed in clojure & contrib: Is there a
function that accepts a sequence of [key value] vectors and creates a
map of some sort? Is there a sane way to say "please give me a creator
of the type of this object"? How about a function that accepts a
hash-map as an argument and returns a sorted-map of the entries?
Thanks,
<mike
--
Mike Meyer <m...@mired.org> http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.
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