Question

I am new to Haskell. I am extremely confused about modules, what they are, and how to use them. For example, I created a add.hs file that contains a simple function as follows:

add a b = a + b

There are some test cases in a file called addTestCases.hs, that check for the functionality of add.hs.

I am somehow supposed to load the testcases to GHC, which will automatically run, and find the add.hs function.

I am really not sure how to accomplish this, and would appreciate any clarification, as I have spent a lot of time trying to figure this out.

Many thanks in advance.

Answer 1

In Add.hs you declare the module name:

-- Notice the module name matches the file name, this is typically required
module Add where

add :: Integer -> Integer -> Integer
add x y = x + y

And in Test.hs you tell it which modules the functions come from:

-- Notice we didn't declare a module name, so it defaults to 'Main'
import Add
import Test.QuickCheck
main = quickCheck (\ x y -> x > 0 && y > 0 ==> add x y > x && add x y > y)

You can now compile and run your tests:

$ ghc Test.hs
[1 of 2] Compiling Add              ( Add.hs, Add.o )
[2 of 2] Compiling Main             ( Test.hs, Test.o )
Linking Test ...
$ ./Test
+++ OK, passed 100 tests.

EDIT:

And if you are working inside of GHCi, and vs compiling from a terminal as shown above, then you can do:

... run "ghci Test.hs" ...
> main
+++ OK, passed 100 tests.