8 May
2009
8 May
'09
2:45 a.m.
Nikhil Patil wrote:
Hi,
I am curious to know if there is a function in Haskell to find if a certain value has already been evaluated. The function I need would have the type:
(?!) :: a -> Bool
I will call this function `evaluated', since it is not a binary operator.
The existence of such a function would violate referential transparency.
What would the value of
( evaluated (fibs !! 100), evaluated (fibs !! 100) )
be ? Suppose that I first print the `fst' of this tuple, then print the
101st Fibonacci nummber, and then print the `snd' of this tuple. By lazy
evaluation, one would expect that this yields
False