How can I add an extra flag to Leksah?

Question

How can I add an extra flag to Leksah?

I'm getting this error:

You need -XDeriveDataTypeable to derive an instance ....

Where can I add the extra flag in Leksah?

Answer 1

1. Navigate to Package -> Edit

2. Select the tab 1 Extensions

3. Check the box for the language extension(s) you need
   (EnableExtension DeriveDataTypable)

4. Click Save in the lower right hand corner

Now the package will be compiler with the desired language extension(s)!