Functions in Haskell

Question

I'm new to functional programming. I have a basic question.

I'm using the Hugs interpreter,

I would like to write a function in Haskell; I went though several tutorials, but I'm not getting it.

fact :: Int -> Int
fact n = if n == 0 then
1
else
n * fact (n-1)

This gives me a syntax error :-S

ERROR - Syntax error in input (unexpected `=')

Answer 1

I assume you type this right into the interactive prompt. Sadly, these are relatively primitive in Haskell - complex definitions, such as fact, can't be entered at the prompt, at least not in the same way you'd normally write them.

You need to put function definitions etc. into modules, then load those via (e.g.) :load fact.hs. There are resources for Hugs specifically that provide more information on this and other topic (I used http://cvs.haskell.org/Hugs/pages/hugsman/index.html to check my assumptions).

Also note that indentation matters, so the code won't work the way you posted it here even when in a module. Those tutorials will have correct versions. If not, they're useless and you should forget them.