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When I do something simple in ghci, like the following:
let x = 7 + 2
I expect ghci to give a response of the type that x holds, like:
x :: Integer
When I run ghci, I do not get that the above line. How do I get that response?
669
Note that if you are in GHCI, you can just put :type before your expression to determine the expression's type, or use :set +t to see the type of every expression in GHCI.
We thus see that we make use of two functions here: (&&) :: Bool -> Bool -> Bool , and elem :: (Eq e, Foldable f) => e -> f e -> Bool , we here use e instead of f to avoid "name clashes" with our already defined type variable a .
If you have installed the Haskell Platform, open a terminal and type ghci (the name of the executable of the GHC interpreter) at the command prompt. Alternatively, if you are on Windows, you may choose WinGHCi in the Start menu. And you are presented with a prompt. The Haskell system now attentively awaits your input.
Introduction. GHCi is GHC's interactive environment, in which Haskell expressions can be interactively evaluated and programs can be interpreted.
Use the ghci :t command, like so:
Prelude> let x = 7 + 2
Prelude> :t x
x :: Integer
Prelude>
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