In-place updates
Futhark supports a mechanism for changing the contents of an array without copying the entire array.
def update (A: *[]i32) (i: i32) (v: i32) =
A with [i] = v> update [1,2,3] 0 42[42i32, 2i32, 3i32]The * annotation for the A parameter indicates that the
update function consumes the array, meaning the argument value
may not be used again by the caller. This is checked through
Futhark’s uniqueness type
system.
We can also create a variant of update that does not consume the
array, at the cost of always copying it.
def update_copy (A: []i32) (i: i32) (v: i32) =
copy A with [i] = vThis is observably equivalent to update.
> update_copy [1,2,3] 0 42[42i32, 2i32, 3i32]