Hello, I met strange behavior of let in ghci 7.0.4. The following works well.
:m Data.List let compFst (n1,s1) (n2,s2) = compare n1 n2 maximumBy compFst [(1, "boo"), (3, "foo"), (2, "woo")] (3,"foo")
But if I bind "maximumBy compFst" to "chooseMax" with "let", it causes error:
let chooseMax = maximumBy compFst chooseMax [(1,"boo"),(3,"foo"),(2,"woo")] <interactive>:1:33: No instance for (Num ()) arising from the literal `2' Possible fix: add an instance declaration for (Num ()) In the expression: 2 In the expression: (2, "woo") In the first argument of `chooseMax', namely `[(1, "boo"), (3, "foo"), (2, "woo")]'
It's very strange to me. Why does this happen? ":t" says:
:t maximumBy compFst maximumBy compFst :: Ord a => [(a, t)] -> (a, t) :t chooseMax chooseMax :: [((), t)] -> ((), t)
I'm writing a tutorial of Haskell and I would like to define chooseMax in ghci with "let" without specifying its signature. --Kazu