# values.ludic — L2: a function is a value. `fn(int) -> int` is a type; `fn name` is any
# top-level function's value; a call through a local, a global, a field or an element of a
# function type is an indirect call. A registry can hold behaviour, and a package can take one.
#
# Running it prints:  42 10 25 49 81 1.5 1
program FunctionValues {
  numbers float
  property Kind { name: string = "", use: fn(int) -> int = null }
  function double(x: int) -> int { return x * 2 }
  function square(x: int) -> int { return x * x }
  function half(x: float) -> float { return x / 2.0 }
  var op: fn(int) -> int = null
  function run_with(f: fn(int) -> int, v: int) -> int { return f(v) }
  function pass_on(f: fn(float) -> float) -> fn(float) -> float { return f }
  entry {
    op = fn double
    print(op(21))
    let ops = new []fn(int) -> int
    push(ops, fn double)
    push(ops, fn square)
    for i in 0 .. len(ops) { print(ops[i](5)) }
    let k = new Kind
    k.name = "square"
    k.use = fn square
    print(k.use(7))
    print(run_with(fn square, 9))
    let h = pass_on(fn half)
    print(h(3.0))
    if op != null { print(1) }
  }
}