propchecker.pony

use "debug"

interface box Runner[A, R]
  fun apply(args: A): R^

interface box Generator[A]
  fun apply(): A^

interface box Property[R]
  fun apply(r: R): Bool

class Checker[A, R]
  fun check(r: Runner[A, R], argsGenerator: Generator[A], prop: Property[R]) ? =>
    let res = r.apply(argsGenerator.apply())
    if not prop.apply(consume res) then
      error
    end

primitive Addition
  fun add(x: U32, y: U32) : U64 =>
    x.u64() + y.u64()

actor Main
  new create(env: Env) =>
    let runner = lambda (a: (U32,U32)): U64 => Addition.add(a._1,a._2) end
    let generator = lambda (): (U32,U32) => (1,2) end
    let property = lambda (r: U64): Bool => r == 3 end
    try
      Checker[(U32,U32), U64].create().check(runner, generator, property)
      Debug.out("OK!")      
    else
      Debug.out("hum?")
    end