Adrian Hey wrote:
Pete Kazmier wrote:
I've modified my Norvig spelling corrector to use a trie instead of
Data.Map in the hopes of improving performance. Plus, this is fun and
a great learning exercise for me. Unfortunately, when I load my trie
with a large amount of data, I get a stack overflow. It's unclear to
me why this is happening. I specifically use foldl' to avoid this
situation when building my trie. Could someone shed some light on the
situation for me?
Here is the code:
module Main where
import Data.List (foldl')
import Data.Maybe (maybe, fromMaybe)
import Prelude hiding (lookup)
import qualified Data.Map as M
data Trie a = T (Maybe a) (M.Map Char (Trie a)) deriving (Show)
Try making it strict in the Map field..
> data Trie a = T (Maybe a) !(M.Map Char (Trie a)) deriving (Show)
Hmm, strictness is a slippery thing, so I think you'll also
need to use strict insertion for the Map. I believe such a thing
was added a while back, but with your code you could use
>insertWith fn (k:ks) v (T mv m) = newtrie `seq` T mv (M.insert k
newtrie m)
> where
> oldtrie = M.findWithDefault empty k m
> newtrie = insertWith fn ks v oldtrie
BTW, if you use strict insertion function (insertWith') it shouldn't
be necessary to do a lookup first.
Regards
--
Adrian Hey
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