Size coercions
The Futhark type checker is not very smart, and in some cases is very conservative in how it tracks the sizes of arrays. For example:
def A = [1, 2, 3] ++ [4, 5, 6]As far as the type checker is concerned, A has a completely
unknown size. Using a size coercion we can change the size to be
what we expect:
def B = [1, 2, 3] ++ [4, 5, 6] :> [6]i32Size coercions are checked dynamically, and the program will fail at run-time if the actual size does not match the expected size. The rank or element type of the array may not change - only the specific dimensions, and they must be identical at run-time.
See also
Complex ranges, Comparing arrays for equality, Flattening and unflattening arrays.