It works when loaded from file, but not when typed into ghci. Why?

Question

If I put the following 2 lines into foobar.hs

f 1 = 1
f x = f (x-1)

then

$ ghci
> :load foobar.hs
> f 5
1
         


        

Answer 1

The latter binding overrides the former. Use this in ghci:

Prelude> :{
Prelude| let f 1 = 1
Prelude|     f x = f (x-1)
Prelude| :}
Prelude> f 5
1

Or, without the layout:

Prelude> let f 1 = 1; f x = f (x-1)
Prelude> f 5
1