$ runhaskell MyFile.hs Alternatively, runghc (they’re the same thing). ghci MyFile.hs will also start an interactive REPL session with MyFile.hs loaded, but if you want to run a main program then runhaskell is the way to go. It’s probably a good idea to get into the habit of testing parts of your program as isolated … Read more
Is there a way provide type declarations in GHCi? let numUniques’ :: (Eq a) => [a] -> Int; numUniques’ = length . nub Or is there another way to define functions like these which doesn’t require type declarations? If you turn off the monomorphism restriction with -XNoMonomorphismRestriction, it will infer the right type.
The workaround that I know of is using :kind. For instance, ghci> :kind (Container ‘[String,String,String,String,String]) Gives: ( Container ‘[String,String,String,String,String]) :: * While ghci> :kind! (Container ‘[String,String,String,String,String]) Will print something like this: Container ((‘:) * [Char] ((‘:) * [Char] ((‘:) * [Char] ((‘:) * [Char] ((‘:) * [Char] (‘[] *)))))) Officially, of course, you’re asking ghci … Read more
:! run the shell command :! cls under windows :! clear under linux and OS X
This is a known bug. and a good catch! The pull request https://github.com/haskell/haskell-mode/pull/1116/files solves it.
:set -XRankNTypes. The -X part is a compiler switch, by the way, extension is called just RankNTypes.
Most of the time, you can rely on type inference to work out a signature for you. In your example, the following is sufficient: Prelude> let addTwo x y = x + y If you really want a definition with a type signature, or your definition spans over multiple lines, you can do this in … Read more
GHCi now has a multiline-input mode, enabled with :set +m. For example, Prelude> :set +m Prelude> let fac 0 = 1 Prelude| fac n = n * fac (n-1) Prelude| Prelude> fac 10 3628800