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Shape 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 shape coercion we can change the size to be what we expect:

def B = [1,2,3] ++ [4,5,6] :> [6]i32

Shape coercions are checked dynamically, and the program will fail at run-time if the actual shape does not match the expected shape. The rank or element type of the array may not change - only the specific dimensions.

See also

Complex ranges