Issue with nested fluents in effects using USERTYPES_REMOVER compiler

[carladavesa]

Hi,

I’ve encountered an issue when using the USERTYPES_REMOVER in unified-planning, and I’d like to confirm whether this is a bug or a limitation in how effects are expressed.

Here’s a simple example of a problem:

problem = Problem('problem')

Cat = UserType('Cat')
no_cat = Object('no_cat', Cat)
one_cat = Object('one_cat', Cat)
null = Object('null', Cat)
problem.add_objects([no_cat, one_cat, null])

my_cats = Fluent('my_cats', Cat)
plus = Fluent('plus', Cat, c1=Cat, c2=Cat) # returns the sum of the cats

problem.add_fluent(my_cats, default_initial_value=no_cat)
problem.add_fluent(plus, default_initial_value=null)

problem.set_initial_value(plus(no_cat, no_cat), no_cat)
problem.set_initial_value(plus(no_cat, one_cat), one_cat)
problem.set_initial_value(plus(one_cat, no_cat), one_cat)


buy_cat = InstantaneousAction('buy_cat')
buy_cat.add_effect(my_cats, plus(my_cats, one_cat))
problem.add_action(buy_cat)

problem.add_goal(Equals(my_cats, one_cat))

After running USERTYPES_REMOVER, I expected it to handle nested fluents in the action effects. However, the output I get doesn’t include some of the expected effects, such as:

if (my_cats(no_cat) and plus(no_cat, one_cat, one_cat)) then my_cats(one_cat) := true

Instead, the output looks like this:

action buy_cat {
    preconditions = []
    effects = [
      if (my_cats(no_cat) and plus(no_cat, one_cat, no_cat)) then my_cats(no_cat) := true
      if (my_cats(no_cat) and (not plus(no_cat, one_cat, no_cat))) then my_cats(no_cat) := false
      if (my_cats(one_cat) and plus(one_cat, one_cat, one_cat)) then my_cats(one_cat) := true
      if (my_cats(one_cat) and (not plus(one_cat, one_cat, one_cat))) then my_cats(one_cat) := false
      if (my_cats(two_cats) and plus(two_cats, one_cat, two_cats)) then my_cats(two_cats) := true
      if (my_cats(two_cats) and (not plus(two_cats, one_cat, two_cats))) then my_cats(two_cats) := false
    ]
}

This output omits the necessary effect for transitioning from my_cats(no_cat) to my_cats(one_cat). The first effect that should apply is missing.

Are nested fluents not supported, or is this a bug in the way the compiler processes such effects? I’d appreciate guidance on whether this is a known limitation or not.

Thanks!

[alvalentini]

Hi @carladavesa, can you report the compiled problem?

[carladavesa]

problem name = utfr_problem

types = [Cat]

fluents = [
  bool my_cats[cat=Cat]
  bool plus[c1=Cat, c2=Cat, cat=Cat]
]

actions = [
  action buy_cat {
    preconditions = [
    ]
    effects = [
      if (my_cats(no_cat) and plus(no_cat, one_cat, no_cat)) then my_cats(no_cat) := true
      if (my_cats(no_cat) and (not plus(no_cat, one_cat, no_cat))) then my_cats(no_cat) := false
      if (my_cats(one_cat) and plus(one_cat, one_cat, one_cat)) then my_cats(one_cat) := true
      if (my_cats(one_cat) and (not plus(one_cat, one_cat, one_cat))) then my_cats(one_cat) := false
      if (my_cats(null) and plus(null, one_cat, null)) then my_cats(null) := true
      if (my_cats(null) and (not plus(null, one_cat, null))) then my_cats(null) := false
    ]
  }
]

objects = [
  Cat: [no_cat, one_cat, null]
]

initial fluents default = [
]

initial values = [
  plus(no_cat, no_cat, no_cat) := true
  plus(no_cat, no_cat, one_cat) := false
  plus(no_cat, no_cat, null) := false
  plus(no_cat, one_cat, no_cat) := false
  plus(no_cat, one_cat, one_cat) := true
  plus(no_cat, one_cat, null) := false
  plus(one_cat, no_cat, no_cat) := false
  plus(one_cat, no_cat, one_cat) := true
  plus(one_cat, no_cat, null) := false
  my_cats(no_cat) := true
  my_cats(one_cat) := false
  my_cats(null) := false
  plus(null, no_cat, no_cat) := false
  plus(null, no_cat, one_cat) := false
  plus(null, no_cat, null) := true
  plus(one_cat, one_cat, no_cat) := false
  plus(one_cat, one_cat, one_cat) := false
  plus(one_cat, one_cat, null) := true
  plus(null, one_cat, no_cat) := false
  plus(null, one_cat, one_cat) := false
  plus(null, one_cat, null) := true
  plus(no_cat, null, no_cat) := false
  plus(no_cat, null, one_cat) := false
  plus(no_cat, null, null) := true
  plus(one_cat, null, no_cat) := false
  plus(one_cat, null, one_cat) := false
  plus(one_cat, null, null) := true
  plus(null, null, no_cat) := false
  plus(null, null, one_cat) := false
  plus(null, null, null) := true
]

goals = [
  my_cats(one_cat)
]

[carladavesa]

problem name = utfr_problem

types = [Cat]

fluents = [
  bool my_cats[cat=Cat]
  bool plus[c1=Cat, c2=Cat, cat=Cat]
]

actions = [
  action buy_cat {
    preconditions = [
    ]
    effects = [
      if (my_cats(no_cat) and plus(no_cat, one_cat, no_cat)) then my_cats(no_cat) := true
      if (my_cats(no_cat) and (not plus(no_cat, one_cat, no_cat))) then my_cats(no_cat) := false
      if (my_cats(one_cat) and plus(one_cat, one_cat, one_cat)) then my_cats(one_cat) := true
      if (my_cats(one_cat) and (not plus(one_cat, one_cat, one_cat))) then my_cats(one_cat) := false
      if (my_cats(two_cats) and plus(two_cats, one_cat, two_cats)) then my_cats(two_cats) := true
      if (my_cats(two_cats) and (not plus(two_cats, one_cat, two_cats))) then my_cats(two_cats) := false
    ]
  }
]

objects = [
  Cat: [no_cat, one_cat, two_cats]
]

initial fluents default = [
]

initial values = [
  plus(no_cat, no_cat, no_cat) := true
  plus(no_cat, no_cat, one_cat) := false
  plus(no_cat, no_cat, two_cats) := false
  plus(no_cat, one_cat, no_cat) := false
  plus(no_cat, one_cat, one_cat) := true
  plus(no_cat, one_cat, two_cats) := false
  plus(one_cat, no_cat, no_cat) := false
  plus(one_cat, no_cat, one_cat) := true
  plus(one_cat, no_cat, two_cats) := false
  plus(one_cat, one_cat, no_cat) := false
  plus(one_cat, one_cat, one_cat) := false
  plus(one_cat, one_cat, two_cats) := true
  plus(two_cats, no_cat, no_cat) := false
  plus(two_cats, no_cat, one_cat) := false
  plus(two_cats, no_cat, two_cats) := true
  plus(no_cat, two_cats, no_cat) := false
  plus(no_cat, two_cats, one_cat) := false
  plus(no_cat, two_cats, two_cats) := true
  my_cats(no_cat) := true
  my_cats(one_cat) := false
  my_cats(two_cats) := false
  plus(two_cats, one_cat, no_cat) := false
  plus(two_cats, one_cat, one_cat) := false
  plus(two_cats, one_cat, two_cats) := false
  plus(one_cat, two_cats, no_cat) := false
  plus(one_cat, two_cats, one_cat) := false
  plus(one_cat, two_cats, two_cats) := false
  plus(two_cats, two_cats, no_cat) := false
  plus(two_cats, two_cats, one_cat) := false
  plus(two_cats, two_cats, two_cats) := false
]

goals = [
  my_cats(two_cats)
]

[alvalentini]

I confirm that this compiler doesn't correctly handle nested fluents.

If I update the action in this way it seems to work fine:

buy_cat = InstantaneousAction('buy_cat', p=Cat)
buy_cat.add_precondition(Equals(my_cats, buy_cat.p))
buy_cat.add_effect(my_cats, plus(buy_cat.p, one_cat))

This is an issue because we should at least raise a meaningful exception in this case.

Thanks for pointing it out.

[carladavesa]

Does that mean that it should work as I pointed out? Or it shouldn't and the solution is to raise an exception?
What is the correct way for it to work?

Thanks so much