Haskell - importing functions from prelude

Question

I have kind of a newbie question. I want to use some functions from prelude, but I'm getting same error all the time.

For example:

Undefined variable "diff"

Some other functions are working, some not. I guess I have to import something, Google didn't help me... I'm using WinHugs.

Answer 1

Here are two sites you should bookmark, because they'll help you find functions you need -- and find out what you need to import.

http://haskell.org/hoogle/ http://holumbus.fh-wedel.de/hayoo/hayoo.html

Searching both those sites, I don't see anything that looks like the function you want. Some possibilities that occur to me are:

• You're learning from a book that has examples of things you'd type at the Linux command line. "diff" is a common Linux command for comparing two files. I believe the windows equivalent is comp.

• You're using some sample code that you got somewhere, but you didn't import everything you needed. If you can find the file that contains the "diff" function, import that.

• You've written a function called "diff", and put it in another file. In the file where you want to use "diff", you need to import the module that contains it.

Answer 2

Prelude is typically imported implicitly. Are you sure that is really your problem? Undefined variable "diff" is a bit vague, since I don't know of a diff function imported with Prelude. Can you elaborate?