On Thu, Mar 22, 2012 at 11:44 AM, Jan Erik Moström
Hi,
I've just started to learn Haskell and played around a bit and tried this
1: let x = [1,2,3] 2: let x = x ++ [4,5,6] 3: x
The last line doesn't give a result. I assume that this is because 'x' is a name of a value, in the second line I redefine 'x' to a new value but Haskell doesn't evaluate the value until the last line but then 'x' becomes recursively defined in itself (the second x on line 2 is interpreted to refer to the value of the first x on line 2 and not the value defined in line 1). This behavior is caused by the lazy evaluation in Haskell.
Have I understood this correctly?
Your conclusion is correct, but your reasoning is not. It's not due to lazyness that x is recursively defined, it's because of the scope. When you type your second x on the second line, that x will refer to the closest (in scope) definition of something called x -- which is the the definition of x on the second line itself. Cheers, -- Felipe.