Haskell by Example: Maps

original

import Data.Map (Map, (!))
import qualified Data.Map as Map

main = do
    let m0 = Map.empty
    let m1 = Map.insert "k1" 7 m0
    let m  = Map.insert "k2" 13 m1
    putStrLn $ "map: " ++ show m

    let v1 = m ! "k1"
    putStrLn $ "v1: " ++ show v1
    putStrLn $ "len: " ++ show (Map.size m)

    let m' = Map.delete "k2" m
    putStrLn $ "map: " ++ show m'

    let prs = Map.lookup "k2" m'
    putStrLn $ "prs: " ++ show prs

    let n = Map.fromList [("foo", 1), ("bar", 2)]
    putStrLn $ "map: " ++ show n

$ runhaskell maps.hs
map: fromList [("k1",7),("k2",13)]
v1: 7
len: 2
map: fromList [("k1",7)]
prs: Nothing
map: fromList [("bar",2),("foo",1)]

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