alloy

问题 Some Request for Comments (RFCs) have these two rules: 1. Each comma character must be escaped with a backslash. 2. A backslash that is not being used to escape a comma must be escaped with a backslash. Here are valid values: A\,B A\\\,B A\\\\\\\,B Here are invalid values: A\\,B A,B A\\\B I created two Alloy models. My second Alloy model has two signatures for backslashes: sig Backslash extends Char {} sig EscapedBackslash extends Char {} The latter, of course, represents a double backslash.

问题 I have two set comprehension predicates (uniary) as bellow in Alloy: pred A (o : Object){ .. } pred B (o : Object) { ..} I would like to define predicates, one of which is disjoint union and another one is Cartesian product of A and B. PS: To define their union and intersection I can define the following predicate: pred Union(o : Object){ A[o] or B[o] } pred Inter(o:Object){ A[o] and B[o] } I would like to get similar predicates for Cartesian product and disjoint union. Thanks 回答1: You may be

问题 Suppose there are 8 pcs and 1 switch, I want to divide three subnets.how to use alloy language program?Can you give an example? 回答1: The following models a small network. sig IP {} some sig Subnet { range : some IP } abstract sig Node { ips : some IP } sig Router extends Node { subnets : IP -> lone Subnet } { ips = subnets.Subnet all subnet : Subnet { lone subnets.subnet subnets.subnet in subnet.range } } sig PC extends Node {} { one ips } let routes = { disj s1, s2 : Subnet | some r : Router

问题 next is a binary relation. This string: A\\\,B is modeled by this next table: Consider the first column of the first row of the table. It's value is A. From A we can get to Backslash0, then Backslash1, then Backslash2, then Backslash3, then Comma0, and then B. So, the number of Backslashes between A and the first reachable non-backslash value (which in this case is Comma0) is an odd number (3). Yea! That is what I want. If the first reachable non-backslash value was a non-comma, then the

问题 I have the following signatures: sig Id, Grade {} sig Foo { result : Id -> Grade } Now I want to create a function that takes in a foo variable and returns all associating Foo -> Grade relationships: fun results[ id : Id ]: Foo -> Grade { //return all Foo->Grade binary relationships such that "id -> grade" in Foo.result } i.e. So if the "result" relationship is like this: (foo0, id0, grade0) (foo0, id1, grade0) (foo0, id2, grade1) (foo1, id0, grade2) (foo1, id3, grade3) (foo2, id0, grade0)

问题 I'm trying to get my feet wet with Alloy (also relatively new-ish to formal logic as well), and I'm trying to start with a completely connected graph of nodes. sig Node { adj : set Node } fact { adj = ~adj -- symmetrical no iden & adj -- no loops all n : Node | Node in n.*adj -- connected } pred ex { } run ex for exactly 3 Node As you can see from the image, Nodes 0 and 1 aren't connected. I thought that my fact was enough to make it completely connected...but perhaps I missed something. 回答1:

问题 I have an alloy model in avlTree.als. This model uses integer arithmetic, specifically the plus and minus functions. This model has some assertions in it, and I can run those just fine using the Alloy Analyzer GUI. I have another alloy model in test.als. This model imports avlTree (using "open avlTree") and then has some assertions about the relations in the avlTree model. But when I try to run these assertions in the Alloy Analyzer GUI, I get the following message: A syntax error has

问题 I have been interested in formal methods for some time. I have used formal methods to reason about some very specific sub-areas of a few projects I have been working on. I was never able to convince other team members to try the same let alone specify an entire domain with a formal method. One method I have found particularly interesting is Alloy. I think that it may "scale" better as foundation for an entire project because it is conceptually and notationally very close to actual programming

问题 When debugging a perplexing problem in Alloy, I've used the evaluator to do 3 > 10 and get the result true . Am I missing something?! 回答1: Alloy integers are typically very narrow by normal standards, and they normally have a sort of 'wraparound' semantics. In the default scope, in Alloy 4.2 Int ranges from -8 to 7, and literal 8, 9, 10 are indistinguishable from literal -8, -7, -6. (The use of out-of-range values like literal 10 cannot be detected statically, because in principle Alloy

问题 I'm interested in using the String type of Alloy, (especially due to the fact it allows the use of special character). I noticed that in order to add a given String to an instance, it is sufficient to include it in an expression. e.g. fact stringInsert{ none!="a"+"b"+"c" } will lead to the creation of atoms "a","b" and "c" in any generated instances. Now my question is, is there a way to declare a pool of strings,defining all possible string atoms that might occur in satisfiable instances,