I have a house with rooms that are defined with connections for when you can go from one room to another eg.
connection(garage,sidehall).
connection(sidehall,kitchen).
connection(kitchen,diningroom).
canget(X,Y):-connection(X,Y).
canget(X,Y):-connection(X,_),
write('player goes from '),write(X),write(' to '),write(Y),nl,
canget(_,Y).
Im trying to figure out how make it so the player can only get from one room to another when they have a specific item, such as you can only be in the kitchen when items = gloves.
canget(X,Y,Item):-connection(X,Y,Item),canbein(Y,Item).
canget(X,Y,Item):-connection(X,Somewhere,Item),canbein(Somewhere,Item),canget(Somewhere,Y,Item).
tried defining canbein with:
canbein(kitchen):- item(sword).
canbein(sidehall):- item(hat).
but that doesnt work!
Have defined my items as such, not sure if this is right either:
item(gloves,sword,helm,cheese).
Basically, have i declared my item values correctly?
How can i use the specific item value to make canget x to y false?
Thank you!
Well, I see a few problems with your code. Firstly, you call canbein with two arguments (from canget predicate). However, canbein is defined as single-argument predicate. Therefore, the call always fails as no canbein/2 predicate exists.
I suggest the following modification:
canbein(kitchen, sword).
canbein(sidehall, hat).
Than, the item definition is not required. Let's think about what happens during the unification of
canget(X,Y,Item) :- connection(X,Y,Item), canbein(Y,Item).
Let's assume the following setting X=sidehall, Y=kitchen, Item==sword. This predicate should be OK. Assuming the conection predicate is OK, prolog tries to find canbein(Y, Item) i.e. canbein(kitchen, sword) and it succeeds.
On the contrary, if the Item is different the unification fails, hence it works as expected.
The second problem is the item predicate. By your definition, it expects 4 arguments. That's nonsense, of course. You should declare it like
item(gloves).
item(sword).
item(helm).
item(cheese).
However, I don't think this predicate is necessary at all. Just to be clear, try to call item(X) and obtain all results (the four declared). Try it with the prior definition - what should you even ask for?
I hope it helps :)
Related
I would like to change the behavior of menhir's output in follwoing way:
I want it to look up all grammatical alternatives if it finds any, and put them in a list and get me back this ambigouus interpretation. It shall not reduce conflicts, just store them.
In the source code of menhir, it seems to me, that I have to look in "Engine.ml". The resultant syntactically determined token comes in a variant type item "Accepted v" as a state of a checkpoint of the grammatical automaton. This content is found by a function "accept env prod" before, that is part of a bundle of recursive functions, that change the states.
Do you have a tip, how I could change these functions to put all the possible results in the list here and proceed as if nothing happened? Or do you think, that this wont work anyway?
Thanks.
What you are looking for is a GLR parser generator (G is for generalized). Menhir is not such tool, and I doubt you could modify it easily to do what you want.
However, there is another tool that does exactly what you want: dypgen.
In boto3 there's a function:
ec2.instances.filter()
The documentation:
http://boto3.readthedocs.org/en/latest/reference/services/ec2.html#instance
Say it returns a list(ec2.Instance) I wish...
when I try printing the return I get this:
ec2.instancesCollection(ec2.ServiceResource(), ec2.Instance)
I've tried searching for any mention of an ec2.instanceCollection, but the only thing I found was something similar for ruby.
I'd like to iterate through this instanceCollection so I can see how big it is, what machines are present and things like that.
Problem is I have no idea how it works, and when it's empty iteration doesn't work at all(It throws an error)
The filter method does not return a list, it returns an iterable. This is basically a Python generator that will produce the desired results on demand in an efficient way.
You can use this iterator in a loop like this:
for instance in ec2.instances.filter():
# do something with instance
or if you really want a list you can turn the iterator into a list with:
instances = list(ec2.instances.filter())
I'm adding this answer because 5 years later I had the same question and went round in circles trying to find the answer.
First off, the return type in the documentation is wrong (still). As you say, it states that the return type is: list(ec2.Instance)
where it should be:ec2.instancesCollection.
At the time of writing there's an open issue in github covering this - https://github.com/boto/boto3/issues/2000.
When you call the filter method a ResourceCollection is created for the particular type of resource against which you called the method. In this case the resource type is instance which gives an instancesCollection. You can see the code for the ResourceCollection superclass of instancesCollection here:
https://github.com/boto/boto3/blob/develop/boto3/resources/collection.py
The documentation here gives an overview of the collections: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/collections.html
To get to how to use it and actually answer your question, what I did was to turn the iterator into a list and iterate over the list if the size is > 0.
testList = list(ec2.instances.filter(Filters=filters))
if len(testList) > 0;
for item in testList;
.
.
.
This may well not be the best way of doing it but it worked for me.
So my task is to write some properties to check the correctness of an insert function for a BST.
Here is the stub code.
My issue is determining what it is I actually need to do.
I've deduced the correct way to insert into the BST is to insert at the proper place (to preserve BST property) and to allow duplicates to be inserted.
Can you help me determine what each property means? Here are my current thoughts:
prop_insert_preserves_bst insertFunction integer
This means check that the structure of the BST is correct. That is, each element is in the proper place and all elements in the left branch have lower values and all elements in the right branch have higher values.
prop_insert_adds_element insertFunction integer
I am confused about this one. Originally I just checked that the new tree (after insertion) container integer. Now I actually check that the new tree is 1 length longer and has 1 new element which is integer.
prop_insert_does_not_change_other_elements insertFunction integer newInteger
For this one I checked that every element in new tree is same as original tree. However I have no idea what newInteger is, I didn't use it in my implementation.
prop_insert_duplicate_check insertFunction integer
This was is even more confusing. Right now I have implemented it in the same way as prop_insert_duplicate_check insertFunction integer. Does it mean that duplicates are accepted and inserted into the tree? (Remember that insertBST function is correct and so must pass all of these properties).
You should check with whoever gave you the exercise!
But anyway, I think you're right for the first two. First one, you check that if isBST is true on a Leaf, it's still true after inserting the given integer. Second one, you check has you said the length and the presence of the inserted integer.
For the third one, you insert the first integer, then newInteger and check integer is still present.
For the fourth one, you need to insert the integer twice and check the results are expected. It does look like the current code does not check for duplicates, are you sure you shouldn't fix the insertBST function? If that's right, you need to check the side arguments, if not you need to check inserting twice produced the same tree as inserting once.
Hope this helps.
I've just started doing work on ontologies with Protegé and I'm trying to understand how to use SWRL rules. I'm afraid I don't get the concept or how to correctly treat them, as I'm not able to produce any output. I'll explain a bit more a simple case I created to test this:
I've created three individuals, called A, B and C. Each one with a test property, that has a boolean range. On the property assertions tab of each one I've initialized their values, so they are test(A,true), test(B,true) and test(C,true). To test how rules work, I created a rule like this: test(A,true), test(B,true) -> test(C,false). The way I understand it is that, if A and B's test property is true, C's one would turn false. To do so, I start the reasoner (Pellet) but nothing happens. I mean, it says the reasoner is active and no "inconsistent ontology" messages appear, but C's test value doesn't change. I'm sure this must be a really simple confusion but I can't seem to find it anywhere nor check if the rule has been activated.
Thank you in advance.
The inference doesnt work like that, you cannot retract test(C, true) if you've asserted it. Your ontology probably includes both test(C, true) and test(C, false) which is completely legal unless you've specified otherwise; in which case then you'd see the inconsistency.
NOTE: The scenario is using 2 entity framework models to sync data between 2 databases, but I'd imagine this is applicable to other scenarios. One could try tackling this on the EF side as well (like in this SO question) but I wanted to see if AutoMapper could handle it out-of-the-box
I'm trying to figure out if AutoMapper can (easily :) compare the source and dest values (when using it to sync to an existing object) and do the copy only if the values are different (based on Equals by default, potentially passing in a Func, like if I decided to do String.Equals with StringComparison.OrdinalIgnoreCase for some particular pair of values). At least for my scenario, I'm fine if it's restricted to just the TSource == TDest case (I'll be syncing over int's, string's, etc, so I don't think I'll need any type converters involved)
Looking through the samples and tests, the closest thing seems to be conditional mapping (src\UnitTests\ConditionalMapping.cs), and I would use the Condition overload that takes the Func (since the other overload isn't sufficient, as we need the dest information too). That certainly looks on the surface like it would work fine (I haven't actually used it yet), but I would end up with specifying this for every member (although I'm guessing I could define a small number of actions/methods and at least reuse them instead of having N different lambdas).
Is this the simplest available route (outside of changing AutoMapper) for getting a 'only copy if source and dest values are different' or is there another way I'm not seeing? If it is the simplest route, has this already been done before elsewhere? It certainly feels like I'm likely reinventing a wheel here. :)
Chuck Norris (formerly known as Omu? :) already answered this, but via comments, so just answering and accepting to repeat what he said.
#James Manning you would have to inherit ConventionInjection, override
the Match method and write there return c.SourceProp.Name =
c.TargetProp.Name && c.SourceProp.Value != c.TargetProp.Value and
after use it target.InjectFrom(source);
In my particular case, since I had a couple of other needs for it anyway, I just customized the EF4 code generation to include the check for whether the new value is the same as the current value (for scalars) which takes care of the issue with doing a 'conditional' copy - now I can use Automapper or ValueInject or whatever as-is. :)
For anyone interested in the change, when you get the default *.tt file, the simplest way to make this change (at least that I could tell) was to find the 2 lines like:
if (ef.IsKey(primitiveProperty))
and change both to be something like:
if (ef.IsKey(primitiveProperty) || true) // we always want the setter to include checking for the target value already being set