[username223]

It's a wash. To understand that thing you posted, I'd have to look up what the exclamation point does to "yield", why adding it forces you to repeat the function name, and whether those "|>" sequences are typos or some weird operator. The other version has some random StudlyCaps, I have to look up. Meh.

[codygman]

Well it's only a wash if you are familiar with one and not the other (and that's the case IIUC). You don't intuitively know what the C# version does either.

For future reference "|>" like "$" in haskell is just short hand for a start and end parenthesis and end of expression or next instance of "|>" or "$".

So in Haskell:

    sum $ filter (> 2) [0..10]

is a less noisy way of saying:

    sum(filter (>2) [0..10])

About the exclamation points, I believe it causes it to evaluate and has to do with ensuring the expression is evalauted. At least that is the case in haskell.

[fleitz]

Imperative / shell programmers may be more familiar with |> as a pipe.

  echo "Hello World" | wc -c

  let wc x:String =
    x.length
  "Hello World" |> wc

are equivalent

[platz]

|> would be the flip of $ since the arg comes before the function

[dllthomas]

So equivalent to Control.Lens.(&)

[Chattered]

yield and yield! are both keywords used in sequence expressions. To compute a sequence of type seq<'T>, you can use a sequence expression, in which the yield keyword takes a value of type 'T, and adds that value to the computed sequence, while yield! takes a value of type seq<'T> and appends that value to the computed sequence.

You also have keywords "return" and "return!" for F#'s version of monads. In Haskell, "return" is just a function, while "return!" is not needed (though I wish it was present in Scala).

[profquail]

In F#, yield emits a new element in the sequence (just as in C#), while yield! emits all of the elements from another sequence you provide. This effectively allows you to "splice" sequences together, or create a new sequence by prepending/appending some elements to an existing sequence.

As another commenter mentioned below, yield! has nothing to do with repeating the function name -- the name is repeated because it's a recursive function (i.e., a function which calls itself). So the sqrtGuesses function produces a sequence which emits (yields) the value it's given (x), computes the next value of x, stores it in the variable next_x, then emits all of the values in the sequence produced by calling sqrtGuesses for the next value of x (next_x).

The |> is called the "forward pipeline operator" in F#, and it's very simple -- whereas you normally call a function f with a value x by writing f x, you can swap the order of the arguments with |> to write x |> f. This effectively allows you to write nested function applications without all of the parentheses: f(g(h(x)) can instead be written x |> h |> g |> f or h x |> g |> f or whatever.

[Chattered]

The function name is repeated because it's recursive!