.net - is there any difference between reduce and reduceBack -

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i'm learning f# msdn , looking , trying out reduce , reduce back, can't find difference, signature same

('t -> 't -> 't) -> 't list -> 't

and both throw same error on empty list, why there 2 of them, there should difference

others explained difference - reduce elements in different order.

for of operations can use reduce or reduceback, difference not matter. in more mathematical terms, if operation associative (such numeric operations, max, min or sum functions, list concatenation, etc.) 2 behave same.

an example can nicely see difference building tree, because shows how evaluation works:

type tree =    | leaf of int   | node of tree * tree  [ n in 0 .. 3 -> leaf n] |> list.reduce (fun b -> node(a, b))  [ n in 0 .. 3 -> leaf n] |> list.reduceback (fun b -> node(a, b))

here 2 trees result (but note if flatten them, same list!)

          reduce        reduceback ------------------------------------- tree:       /\              /\            /\ 3            0 /\           /\ 2              1 /\          0  1                2  3 ------------------------------------- flat:    0 1 2 3          0 1 2 3

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