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Argument order of andMap #129

@yardsale8

Description

@yardsale8

I find the argument order of andMap curious. Most maps have the function(s) preceding the data, which facilitates piping with maps.

xs 
 |> func1
 |> map func2
 |> func3

The current argument order means including andMap in a pipe is awkward.

xs 
 |> f
 |> \d -> andMap d gs
 |> h

It seems to me that this function would be more useful with the arguments in the opposite order.

data
|> f
|> andMap gs
|> h

What are the advantages of current implementation? Would it be possible to switch the order?

Motivation for the change

I frequently find myself performing programming origami by unfolding data, applying a sequence of functions to each component, then folding the data back together. Swapping the argument order of andMap facilitates this style of programming.

data
  |> unfold
  |> andMap doStuff
  |> fold

For example, suppose I am making a string representation of a record of type {x : Int, y : Float}. The brute force solution

makeStr r =
[ "{"
, r |> .x |> String.fromInt
, ", "
, r |> .y |> String.fromFloat
, "}"
] |> String.join " "

involves two similar, but necessarily different, pipes. Using the origami approach, this refactors into

-- helpers
xToStr = .x << String.fromInt
yToStr = .y << String.fromFloat
wrapRecord s = "{" ++ s ++ "}"

makeStr r =
  r
  |> repeat 2                --unfold
  |> andMap [xToStr, yToStr] --doStuff
  |> String.join ", "        --fold
  |> wrapRecord

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