Is it possible to define an F# operator that applies multiple functions to a single argument (almost the opposite of the ||> operator)?

Question

My attempt to do this is here (forgive the for loop - I was just curious to see if this was possible):

let (|>>) a (b : ('a -> unit) list) = 
    for x in b do
        x a

but when I try to use it I get the error

Answer 1

That None of the types error message can occur if the function you're trying to use is defined further down the file or isn't imported correctly. Otherwise, your function definition seems ok.

Answer 2

I would discourage the use of a custom operator for this. I think they should be used very rarely. This one doesn't seem general enough to be worth defining and could make code hard to read. Here is one alternative:

[ printf "%A"; printfn "%A" ] |> List.iter ((|>) 1)

But it's even clearer and shorter to write out your operator definition inline:

for f in [ printf "%A"; printfn "%A" ] do f 1