| type Heap |
| |
| type Bag = { count : U32, sum : U32 } |
| |
| newBag : Heap -> < Failure Heap | Success (Bag, Heap) > |
| |
| freeBag : (Heap, Bag) -> Heap |
| |
| addToBag : (U32, Bag) -> Bag |
| addToBag (x, b { count = c, sum = s }) = b { count = c + 1, sum = s + x } |
| |
| averageBag : Bag! -> < EmptyBag | Success U32 > |
| averageBag b = if b.count == 0 then EmptyBag else Success (b.sum / b.count) |
| |
| type List a |
| |
| reduce : all (a, b). ((List a)!, (a!, b) -> b, b) -> b |
| |
| average : (Heap, (List U32)!) -> (Heap, U32) |
| average (h, ls) = |
| newBag h |
| | Success (bag, h') -> |
| let bag' = reduce (ls, addToBag, bag) |
| in averageBag bag' !bag' |
| | Success n -> (freeBag (h', bag'), n) |
| | EmptyBag -> (freeBag (h', bag'), 0) |
| | Failure h' -> (h', 0) |
| |
