sketch.tn

struct A {
  pub i32 f1
}

impl A {
  (&self)i32 repr = self.f1
}

trait Iterator {
  type Item

  (&mut self)?Self.Item next
}

impl Iterator for A {
  type Item = i32

  (&mut self)?Self.Item next {
    let value = self.f1

    self.f1 = self.f1.saturating_sub 1

    value
  }
}

(type T, type U, T)U force_cast value {
  if !std.canCast T U => @compile_error & @fmt("cannot cast {} to {}", std.typeName T, std.typeName U)

  unsafe { std.force_cast T U value }
}

trait Monad {
  type Item
}

(type A, type B)bool TypeEq = A == B

trait Functor where TypeEq(Self, Self.This[Self.Item]) {
  type Item

  type This[T]: Functor[Item = T]

  (type U, self, impl Fn(Self.Item, Output = U))Self.This[U] fmap
}

trait Applicative: Functor[Item = Self.Item] {
  type Item

  (Self.Item)Self pure
}

trait Semigroup: Functor[Item = Self.Item] {
  type Item

  (self, Self)Self <>
}