2009/9/5 Günther Schmidt
Hi all,
I'm reading in a data of 216k records into a map of Key, Values Pairs, the values being strings.
As it happens out of 216k String values there really are only about 6.6k distinct string values, so I could save a lot of RAM if I was able to "insert" only actually *new* string values into the map and use references to (string) values that already are in memory instead.
Is there a container that would, if I wanted to insert an element, return a pair of either the previously inserted, equal value and the container unchanged, or the new, previously unknown value and the new container amended by that element?
I believe a memoization of the identity function will do what you want: import qualified Data.MemoCombinators as Memo share = Memo.list Memo.char id Then pass any string through share to make/get a cached version. You might want to limit the scope of share -- eg. put it in a where clause for the function where you're using it -- so that it doesn't eat memory for the lifetime of your program, only for when you need it. Luke