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Comment by AdieuToLogic

1 year ago

If anyone is interested in the theoretical background to the thrush combinator, a.k.a. "|>", here is one using Ruby as the implementation language:

https://leanpub.com/combinators/read#leanpub-auto-the-thrush

Being a concept which transcends programming languages, a search for "thrush combinator" will yield examples in several languages.

2 comments

AdieuToLogic

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wslh  1 year ago

I find this [1] from this [2]. Seems like a good explanation. It doesn't exist on Wikipedia though.

[1] https://github.com/raganwald-deprecated/homoiconic/blob/mast...

[2] https://stackoverflow.com/a/285973/88231

  • AdieuToLogic  1 year ago

    A key thing to keep in mind is that the thrush combinator is a fancy name for a simple construct. The semantics it provides is a declarative form of traditional function composition.

    For example, given the expression:

      f (g (h (x)))

    The same can be expressed in languages which support the "|>" infix operator as:

      h (x) |> g |> f

    There are other, equivalent, constructs such as the Cats Arrow[0] type class available in Scala, the same Arrow[1] concept available in Haskell, and the `andThen` method commonly available in many modern programming languages.

    0 - https://typelevel.org/cats/typeclasses/arrow.html

    1 - https://wiki.haskell.org/Arrow_tutorial