Re: [Haskell-cafe] Type inference for lambda function

21 Oct 2021


      On Thu, Oct 21, 2021 at 08:40:45PM +0200, Matthias Güdemann wrote:
...
This is what I get using ghci
λ> :t (\a b -> a + b)
(\a b -> a + b) :: Num a => a -> a -> a
but when loading a .hs file with just this function (without signature)
add = \a b -> a + b
I get
λ> :t add
add :: Integer -> Integer -> Integer
Compare:

    $ ghci -XNoMonomorphismRestriction
    λ> x = \a b -> a + b
    λ> :t x
    x :: Num a => a -> a -> a

with

    $ ghci -XMonomorphismRestriction
    λ> x = \a b -> a + b
    λ> :t x
    x :: Integer -> Integer -> Integer

-- 
    Viktor.

Re: [Haskell-cafe] Type inference for lambda function

Viktor Dukhovni