F# ((*)2) and ((<<<)1) act differently

Question

I have these two pieces of code:

• [| 0 .. N-1 |] |> Array.map((<<<)1)

• [| 0 .. N-1 |] |> Array.map((*)2)

I thought they do absolutely the same things but they don't. In first case I get 1, 2, 4 and in second - 0, 2, 4. I don't understand why there is 1 in the first case? If I write let a = 0 <<< 1, I get 0. Is this a bug? Thanks!

Answer 1

The arguments are not in the order you think, they are the other way around.

Compare it with:

let a = 1 <<< 0 // this is equivalent to ((<<<)1) 0

The first argument after the parenthesized operator is the left argument, not the right.