[TO FIX] does not compile why ?

bower.json

@@ -14,7 +14,8 @@
     "purescript-routing": "^6.1.2",
     "purescript-argonaut-codecs": "^2.0.0",
     "purescript-argonaut-traversals": "^2.0.0",
-    "purescript-argonaut": "^3.1.0"
+    "purescript-argonaut": "^3.1.0",
+    "purescript-random": "^3.0.0"
   },
   "devDependencies": {
     "purescript-psci-support": "^3.0.0"

src/randomText.purs

+module RandomText where
+
+import Prelude
+import Data.String (toCharArray, fromCharArray)
+
+import Data.Maybe(Maybe(Nothing, Just), fromJust)
+import Data.Tuple.Nested ((/\))
+import Data.Tuple(Tuple(..))
+import Data.Array ( length, (!!)
+                  , head  , tail
+                  , take  , takeEnd
+                  , drop  , dropEnd
+                  )
+-- import Control.Monad.Eff.Console (log)
+import Control.Monad.Eff.Random (RANDOM(..), randomInt)
+import Control.Monad.Eff(Eff(..))
+import Partial (crash)
+import Partial.Unsafe (unsafePartial)
+
+
+
+--rando Ran x [] = Ran x []
+--rando Ran x xs = Ran (x <> [x']) (rando xs')
+--    where
+--        Ran x' xs' = randomIt xs
+--
+
+remove :: forall t5. Int -> Array t5 -> Array t5
+remove n [] = []
+remove n xs = unsafePartial $ case n of
+                   0 -> fromJust $ tail xs
+                   _ -> (take n xs) <> (drop (n+1) xs)
+
+
+data Ran  = Ran  { l :: Char, r :: Array Char}
+
+randomIt :: forall t46. String -> Eff ( random :: RANDOM | t46 ) Ran
+randomIt ar = unsafePartial $ do
+    let ar' = toCharArray ar
+    n    <- randomInt 0 (length ar' - 1)
+
+    let maybeChar = (ar' !! n )
+    let rest   = remove n ar'
+
+    case maybeChar of
+         Nothing    -> crash "it should not happen"
+         Just char  -> (Ran char rest) -- (Ran char rest)
+
+randomText :: String -> String
+randomText txt = fromCharArray ( start <> middle <> end)
+        where
+            txt'   = toCharArray        txt
+            start  = take 2             txt'
+            middle = dropEnd 2 $ drop 2 txt'
+            end    = takeEnd 2          txt'
+
+testText :: String -> String
+testText txt = case (length (toCharArray txt)) >= 5 of
+                    true -> randomText txt
+                    _    -> txt