AttributeError: '_UserType' object has no attribute 'type' about unified-planning

[alvalentini]

This is due to the fact that we changed the way you can create a Fluent.
Now you have to specify also the name of the parameters, not only the type.

In order to create the fluent At you can create it in one of the following way:

• at = Fluent("At", BoolType(), loc=Location)
• at = Fluent("At", BoolType(), [Parameter('loc', Location)])
• at = Fluent("At", BoolType(), OrderedDict([('loc', Location)]))

Let me know if this can solve your problem.

[mikand]

@alvalentini is right, however we should try to give a more meaningful error (if possible)

[alexander-sung]

Nice. Thank you very much for the quick reply, @alvalentini. I assumed it was an interface change but looked at the wrong place. With your directions it is now clear that the type parameters of a fluent shall have names, which was missing in my old example. Bear with me, I surely still have a lot to catch up and thus very welcome Andrea's suggestion.

[alexander-sung]

Nice. Thank you very much for the quick reply, @alvalentini. I assumed it was an interface change but looked at the wrong place. With your directions it is now clear that the type parameters of a fluent shall have names, which was missing in my old example. Bear with me, I surely still have a lot to catch up and thus very welcome Andrea's suggestion.

[alexander-sung]

Sorry, I have a follow-up on this: Is it important that the user is providing specific parameter names? I'm just updating my examples and at some point create generic names, e.g., OrderedDict([(f"parameter{index}", Location) for index in range(3)]). So, I wondered if this is something you wanted to avoid.

I guess it depends on whether the user wants to use these parameter names at some point and might wonder what they are.

[alvalentini]

The parameter names are useful for documentation reasons (similarly to PDDL): they can explain the semantic of the parameters.

They can make easier to understand the problem you are modeling, reading the python code you wrote.

[alexander-sung]

Makes sense. In my simple examples, it's rather obvious from the UserType but documentation is good. Many thanks again for your support! I really appreciate it.