On Apr 25, 2014, at 4:16 AM, Herbert Valerio Riedel
Hello Richard,
On 2014-04-24 at 15:04:55 +0200, Richard Eisenberg wrote:
That map seems to store the set of variables during printing TH, for the purposes of disambiguating identifiers with the same name but different uniques. If blatting out a whole lot of program text, I could imagine the Map getting somewhat sizeable.
When does printing TH actually occur? If it doesn't occur during regular compilation, do we ever need to pretty print large amounts of TH?
I guess it depends on who “we” are. In the process of routine TH hackery, I would say that printing is uncommon -- normally the TH is processed and then just spliced, without user interaction. But, I can conceive of a library that does some processing and then prints.
But, it seems to only need the lookup and insert operations...
Good observation.
actually, it uses a specific combination of lookup+insert, so that it would suffice to have the single operation in the style of Python's dict.setdefault(), i.e.
findWithDefaultInsert :: Ord k => k -> v -> Map k v -> (v, Map k v) findWithDefaultInsert k default m | Just v <- Map.lookup k m = (v, m) | otherwise = default `seq` (default, Map.insert k default m)
is there a simpler data structure that has only these operations efficiently?