promise.md

• Defs:

  • 1. O: All objects
  • 2. P: All objects following the official spec
  • 3. T: All objects with the method then
  • 4. f(x). Return true iif x ⊆ P
  • 5. g(x). Return true iif x ⊆ T
  • 6 eval(x). x ⊆ P iff x resolves in the future
  • 7 eval(x). x !⊆ P iif eval fails

• Test using g(x)

  • Goal: { f(o) = g(o) | o ⊆ O }
  • Try: o = {then() {}}, o ⊆ O, f(o) ≠ g(o)
  • Conclusion: Fails

• Test using eval(x)

  • Goal: { eval(o) | o ⊆ O }
  • Try: x = {then() { sleep(inf) }}, eval(x) never terminates. Fallback proof: "the halting problem"
  • Conclusion: Fails