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testers using alloy
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The development of this site is supported by the National Science Foundation under Computing Research Infrastructure Grant No. 0707612.
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> I see that the existing "write file per found solution" examples are
> xml-specific. But, what if I want to output, say, a double-quoted
> string, or an integer, or a monetary amount?
Yes, your tool can do more specific evaluations also.
The Essai example, as I recall, invokes the alloy compiler's
parseEverything() method to get a pointer to the root of the AST.
He then iterated over each Command defined in the AST,
and for each Command he invokes the executeCommand() method.
If a Command is successful, you'll get an A4Solution object back.
He then simply calls writeXML() on each A4Solution object he gets.
Instead of that, once you get an A4Solution, you can simply evaluate
any part of the AST you wish. For example, suppose your model looks like
abstract sig Person { grades: Int }
one sig Alex, Bob, Cathy extends Person { }
fact { .... }
If you get an A4Solution object back, you can first of all
retrieve the list of Sig from the AST, and you'll see there are Sig
objects named "univ", "Int", "Person", "Alex", "Bob"...
You can go to the Person sig and retrieve its list of fields.
You'll see it has only one field.
Given sol is the A4Solution, a is Alex object, and g is the grades field,
you can call "sol.eval(a.join(g))" to evaluate the result of Alex.grades
The answer will be an Int atom, which you can convert to an integer
and you can then show that to your user.
> A clever alloy modeling approach I saw recently was actually pretty
> simple: if you want text, model the keywords of your language directly
> in alloy sigs (plus a grammar for variable value generation, I am
> presuming). That is the rationale of the alloy2sql module from the ADUSA
> project. Is there any part of alloy2sql that is publicly available? [The
> paper gives only hints at implementation].
You'll have to ask the authors of that project whether they could make the code available.
> Hope the specific windows command lines can help someone,
> and I'd appreciate any advice on my text output questions.
It sounds like a very interesting project. Please let us know how else we can help.
Sincerely,
Felix Chang
Alloy4 Lead Developer