When we call the same function on a list of things, we call that "map". What do we call it when we call a list of functions on the same data? I don't mean pipe - not feeding the output of each function in turn into the next function - but simply iterating over a list of functions, passing each the same input?

  • 5
    In my day, we used to call that "calling a list of functions with the same input."
    – Blrfl
    Jan 4, 2017 at 19:15
  • I think calling "collection" of different methods with same signature(input) is what event and eventhandlers does. When you raise an event all eventhandlers executed with same input parameters. I think "delegating" is ok word.
    – Fabio
    Jan 4, 2017 at 19:56
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    Using Flynn's taxonomy, I would suggest MISD (multiple instruction, single data).
    – mouviciel
    Jan 5, 2017 at 9:34
  • This is a fairly easy example of the Visitor pattern -- maybe you'll find your verbiage researching that. Jan 5, 2017 at 15:38

1 Answer 1


I do not know of any term for your operation, but it can be seen as a kind of mapping, so maybe you do not need a special name for it. I will illustrate this in Haskell, but it is easy to do the same in other languages, e.g. Python, Clojure, Javascript, etc.

In Haskell map has type:

map :: (a -> b) -> [a] -> [b]

For example, you can map length over a list strings:

xs = ["Good", "morning", "world"] :: [String]

> map length xs

Now suppose you have a list of functions, e.g.

fs = [(+ 1), (* 5), (* 2)] :: [Int -> Int]

How can you apply each function to the same number, say, 1? You can use the function:

($) :: (a -> b) -> a -> b

This function takes another function and applies it to an argument. If you partially apply it to the number 1, you get:

($ 1) :: Num a => (a -> b) -> b

This is a function that given a function from a numeric type to any type b, applies it to 1. So, now we can map ($ 1) over our list of functions:

> map ($ 1) fs

So, in general, given an input x :: a and a list of functions fs :: [a -> b] you can apply all the functions to x with map ($ x) fs, which gives you a result of type [b].

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    Excellent. I suspected it was just another variation on map, but couldn't articulate an answer well enough to prove it. Jan 4, 2017 at 19:58

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