A list of combinators

Combinators.swift

func apply<A, B>(fn: (A) -> B, a: A) -> B {
    fn(a)
}

func bluebird<A, B, C>(fn1: (A) -> B, fn2: (C) -> A, c: C) -> B {
    fn1(fn2(c))
}

func blackbird<A, B, C, D>(fn1: (C) -> D, fn2: (A, B) -> C, a: A, b: B) -> D {
    fn1(fn2(a, b))
}

func cardinal<A, B, C>(fn: (A, B) -> C, b: B, a: A) -> C {
    fn(a, b)
}

func dove<A, B, C, D>(fn1: (A, C) -> D, a: A, fn2: (B) -> C, b: B) -> D {
    fn1(a, fn2(b))
}

func finch<A, B, C>(a: A, b: B, fn: (B, A) -> C) -> C {
    fn(b, a)
}

func goldfinch<A, B, C, D>(fn1: (A, B) -> C, fn2: (D) -> B, d: D, a: A) -> C {
    fn1(a, fn2(d))
}

func hummingbird<A, B, C>(fn: (A, B, A) -> C, a: A, b: B) -> C {
    fn(a, b, a)
}

func jay<A, B>(fn1: (A, B) -> B, a1: A, b: B, a2: A) -> B {
    fn1(a1, fn1(a2, b))
}

func kestrel<A, B>(a: A, b: B) -> A {
    a
}

func kite<A, B>(a: A, b: B) -> B {
    b
}

func owl<A, B>(_ fn1: @escaping ((A) -> B) -> A, fn2: (A) -> B) -> B {
    fn2(fn1(fn2))
}

func phoenix<A, B, C, D>(fn1: (A, B) -> C, fn2: (D) -> A, fn3: (D) -> B, d: D) -> C {
    fn1(fn2(d), fn3(d))
}

func psi<A, B, C>(fn1: (A, A) -> B, fn2: (C) -> A, c1: C, c2: C) -> B {
    fn1(fn2(c1), fn2(c2))
}

func queer<A, B, C>(fn1: (A) -> B, fn2: (B) -> C, a: A) -> C {
    fn2(fn1(a))
}

func robin<A, B, C>(a: A, fn: (B, A) -> C, b: B) -> C {
    fn(b, a)
}

func starling<A, B, C>(fn1: (A, B) -> C, fn2: (A) -> B, a: A) -> C {
    fn1(a, fn2(a))
}

func starling<A, B, C>(fn1: (A, B) -> C, fn2: (B) -> A, b: B) -> C {
    fn1(fn2(b), b)
}

func vireo<A, B, C>(a: A, b: B, fn: (A, B) -> C) -> C {
    fn(a, b)
}

func warbler<A, B>(fn1: (A, A) -> B, a: A) -> B {
    fn1(a, a)
}