[Haskell-beginners] Problem with an if statement

[Karol Samborski]

Hi,

With a function defined like this (colors is type of Array Int [Int]
and edges is [Int]):
saturation (_,edges,_) = foldr (\ed ac ->if null (colors!ed) then ac
else ac+1) 0 edges
I'm getting an infinite loop.

But when I remove the if statement like this:
saturation (_,edges,_) = foldr (\ed ac -> ac+1) 0 edges
everything's working.

How should I define my function with the if statement to not getting
an infinite loop?

Best Regards,
Karol Samborski