Using ghci to find type

问题

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?

回答1:

To show types automatically use :set +t:

μ> :set +t
μ> let x = 7 + 2
x :: Integer
μ>

回答2:

Use the ghci :t command, like so:

Prelude> let x = 7 + 2
Prelude> :t x
x :: Integer
Prelude> 

回答3:

To find the type of something in GHCi, you can use the :type command, or (as is much more common), the abbreviated :t. With this, you can do something like:

Prelude> let x = 7 + 2
Prelude> :t x
x :: Integer

来源：https://stackoverflow.com/questions/12659927/using-ghci-to-find-type