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Re-oder aguments of pipeline operator
f#pipeline

Hi all!
In pipeline operator, how to re-order argument of function.
Ex:

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let x = 2 |>(-) 3
// --> x = 3 - 2 . So the value of x is 1

So how to define operator !> to reorder argument of function. Or exist any technique to do like that?

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let x = 2 !>(-) 3
// --> x = 2 - 3 . I would like the value of x is -1.

Thanks you!

.

You could also, prioritize evaluation using parenthesis:

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let x = 2 |> ((-) 3)
//or using partially applied function
let subTo3 = (-) 3 //val subTo3 : (int -> int)
let x = 2 |> subTo3
By on 10/11/2011 6:32 PM ()

Your solution still gives 1, instead of -1. That is because (-) a b translates into a - b.

So with your code:

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let x = 2 |> ((-) 3)

This is equivalent:

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let x = (-) 3 2 // id est: 3 - 2
By on 10/11/2011 7:01 PM ()

Oops, misreading of the question :/

By on 10/12/2011 4:41 PM ()

The problem is not the |> - Operator, but the function on the right of it. |> works with one argument so if you have a function f : 'a -> 'b then the operator is defined as "x |> f := f x (or f(x) if you like)". What you have on the right is curried function op : 'a -> 'b -> 'c and you provide it with one parameter ("3" in your case) to get the desired behaviour.

If you want to switch the parameters you can define a function swap and write

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let swap f a b = f b a
let x = 2 |> (swap (-)) 3

(PS: with Haskells Sections you could more satisfyingly write (+ (-3)) instead of (swap (-)) 3 but sadly F# don't has all the nice syntactic sugar Haskell has (yet?))

By on 7/3/2011 9:21 PM ()

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