Question

How do you build IOVector from MVector? IOVector is documented as:

type IOVector = MVector RealWorld

I have a MVector like below, and will like to construct IOVector (for input to MSV.unsafeWith function – MSV is short-hand for Data.Vector.Storable.Mutable library):

v <- MSV.replicate 5 0 :: (IO (MVector (PrimState IO) CShort)) 

Answer 1

type PrimState IO = RealWorld

(from the primitive package’s source code)

So an MVector (PrimState IO) is an MVector RealWorld and, thus, an IOVector; you can use it directly. IOVector is just a convenience synonym so you don’t have to type out MVector RealWorld all the time 🙂