MonadTests.fs

module Tests

open Xunit
open Swensen.Unquote
open Monad

[<Fact>]
let ``Maybe bind on Just`` () =
    Just 5 >>= (((*) 10) >> return') =! Just 50

[<Fact>]
let ``Maybe fmap on Just`` () =
    ((*) 10) <!> Just 5 =! Just 50

[<Fact>]
let ``Maybe Ap on Just`` () =
    let f x y = x * 100 + y * 10
    f <!> Just 5 <*> Just 2 =! Just 520

[<Fact>]
let ``Maybe comp expr`` () =
    do' {
        return! Just "x"
    } =! Just "x"

[<Fact>]
let ``Maybe comp expr with zero`` () =
    do' {
        let x = 3
        let! y = Just 20
        if false then return x + y
    } =! Nothing

[<Fact>]
let ``Either bind on Right`` () =
    Right 5 >>= (((*) 10) >> return') =! Right 50

[<Fact>]
let ``Either fmap on Right`` () =
    ((*) 10) <!> Right 5 =! Right 50

[<Fact>]
let ``Either Ap on Right`` () =
    let f x y = x * 100 + y * 10
    f <!> Right 5 <*> Right 2 =! Right 520

[<Fact>]
let ``Either Ap on Left`` () =
    let f x y = x * 100 + y * 10
    f <!> Right 5 <*> Left "oops" =! Left "oops"