On 08/03/2010, at 12:17, Alexander Solla wrote:
GHC even optimizes it to:
fib = fib
Sounds like an implementation bug, not an infinite dimensional vector space bug. My guess is that strictness is getting in the way, and forcing what would be a lazy call to fib in the corresponding list code -- fib = 0 : 1 : (zipWith (+) fib (tail fib)) -- into a strict one.
In fact, I'm pretty sure that's what the problem is:
data Vector a = Vector {-# UNPACK #-} !Int {-# UNPACK #-} !Int {-# UNPACK #-} !(Array a)
The problem is that you have to allocate an Array of a specific length when creating a Vector. Arrays are finite by definition. It's not a bug, it's a feature. Note that in the context of package vector, "vector" means a 1-dimensional, 0-indexed array. This is not unusual - see, for instance, the standard C++ library. Roman