[joel_ms]

I got used to this in Haskell, but I have to say that Elm's solution is pretty elegant:

  Elm:               Haskell:

  f <| g <| x   ==   f $ g  $  x    -- application

  f << g        ==   f . g          -- composition

  x |> g |> f   ==   x & g  &  f    -- reverse application

       g >> f   ==       g >>> f    -- reverse composition

It's nice to be able to change between composition and application by changing between | and < in the operator. I've actually done this quite a lot when refactoring code in Elm lately, there's something visual and intutive about it that I like. It makes it easier to mix left-to-right and right-to-left in the same code, while keeping it obvious what's going on.

I've found that certain parts, that scan/read better as imperative steps (think chains of List.map, Maybe.map, <MonadlikeModule>.andThen etc.) often benefit from a reverse application and/or composition. Sort of to simulate the look of do notation since Elm doesn't have that. Smaller functional parts are better with regular application/composition. With the directional operators, this becomes quite ergonomical.

Probaly helps that I use (and enjoy, ymmv) a font with ligatures for these symbols.