Korou Syntax Quick-Stop

korou-syntax-quickstop.hs

-- functions are defined like so
fn add(a: Int, b: Int) -> Int {
  a + b
}

-- effects can be declared like so
effect fail[E] {
  fn fail(ctx: E)
}

-- and used like so
fn divide(a: Int, b: Int) -> Int/fail[Str] {
  if b == 0 {
    "Cannot divide by zero" -> fail;
  }
  a / b
}

-- and handled like so
fn divideOrDefault(a: Int, b: Int, d: Int) -> Int {
  with handle fail[Str] {
    fn fail(ctx: Str) { d }
  } do {
    divide(a, b)
  }
}

-- functions are sugar for continuations
fn add2(a: Int, b: Int, cc: Int ->) {
  a + b -> cc;
}

-- because of this, functions can have multiple return values
fn adjacent(x: Int) -> (Int, Int) {
  x, x
}

-- effects on the return type are sugar as well
fn divide2(a: Int, b: Int, cc: Int/fail[Str] ->)/fail[Str] {
  if b == 0 {
    "Cannot divide by zero" -> fail;
  }
  a / b -> cc;
}

-- closures are defined with { curly braces }
fn addCurried(a: Int) -> (Int -> Int) {
  |b: Int| -> Int { a + b }
}

-- nullary closures are written as blocks
fn orElse(a: Int) -> Int {
  -- type may be written {Int}, () -> Int, or (Int ->) ->
  let incremented: {Int} = {
    a + 1
  };
  if a == 0 {
    a
  } else {
    incremented()
  }
}

-- nullary closures have special sugar when passed as the last argument to a function
fn fix[A](f: ({A}) -> A) -> A {
  f { fix(f) }
}