That looks interesting, I hadn't heard of the project. Will definitely have a look at the library.

But it defines its pipe function the same way RXJS does, separately for any number of arguments:

  function pipe<A>(a: A): A
  function pipe<A, B>(a: A, ab: (a: A) => B): B
  function pipe<A, B, C>(a: A, ab: (a: A) => B, bc: (b: B) => C): C
  function pipe<A, B, C, D>(a: A, ab: (a: A) => B, bc: (b: B) => C, cd: (c: C) => D): D
  ...

https://github.com/gcanti/fp-ts/blob/master/src/function.ts#...