17 Nov
2012
17 Nov
'12
8:57 p.m.
On 12-11-17 02:19 AM, damodar kulkarni wrote:
Let's see tthis: Prelude> :t 3 "a" 3 "a" :: (Num ([Char] -> t)) => t
No complaint from GHC; but now see this:
Prelude> :t "a" 3
<interactive>:1:0: Couldn't match expected type `t1 -> t' against inferred type `[Char]' In the expression: "a" 3
Why does it not fail for (:t 3 "a") but does fail for (:t "a" 3)?
3 is polymorphic, "a" is monomorphic (exactly [Char]). To make "a" polymorphic, turn on OverloadedStrings: :set -XOverloadedStrings :type "a" "a" :: Data.String.IsString a => a :type "a" 3 "a" 3 :: (Num a, Data.String.IsString (a -> t)) => t Success! This is clearly depravity.