Identity Monad for Nim

main.nim

# identity functor and monad for Nim https://hackage.haskell.org/package/base/docs/Data-Functor-Identity.html

type Identity*[T] = object
   runIdentity*: T

# return(unit) for identity
proc identity*[T](a: T): Identity[T] = Identity[T](runIdentity: a)

proc `$`*[T](a: Identity[T]): string = 
    "Identity " & $(a.runIdentity)

# fmap :: Functor f => (a -> b) -> f a -> f b
proc fmap*[A, B](f: proc (i: A): B, i: Identity[A]): Identity[B] {.inline.} = 
    identity[B](f(i.runIdentity))

# (>>=) :: Monad m => m a -> (a -> m b) -> m b
proc `>>=`*[A, B](i: Identity[A], f: proc (a: A): Identity[B]): Identity[B] {.inline.} = 
    f(i.runIdentity)

proc `>>`*[A, B](a: Identity[A], b: Identity[B]): Identity[B] {.inline.} = 
    b

echo identity(10) >> identity(5)
echo identity(10) >>= (proc (x: int): Identity[int] = identity (x + x))