Problem with Comparing Trees

Martin Meyer · Post by **Martin Meyer** » 2 Oct 2016 15:26

Hello Thomas,

please have a look at this construction. It throws error c504: The expression has type 'syntaxDomains::tree{@Type}', which is incompatible with the type 'syntaxDomains::tree{::unsigned}' in (VIP 7502):

Code: Select all

interface syntaxDomains{@Type}
    domains
        tree = tree(subTree* SubTreeList).
        subTree =
            leaf(@Type Value);
            branch(tree Tree).
end interface syntaxDomains
 
 
implement main
    open syntaxDomains{unsigned}
 
    clauses
        run() :-
            Tree1 = tree([]),
            Tree2 = tree([]),
            _Result = toBoolean(Tree1 = Tree2).  %the error is here
end implement main

But the code compiles when replacing Tree1 = Tree2 by Tree1 <> Tree2.

Regards
Martin

Post by **Thomas Linder Puls** » 2 Oct 2016 22:58

We will look at it.

It is a bug, but on the other hand I will advise you to use explicit type parameters in domains instead:

Code: Select all

interface syntaxDomains
 
domains
    tree{T} = tree(subTree{T}* SubTreeList).
    subTree{T} =
        leaf(T Value);
        branch(tree{T} Tree).
 
end interface syntaxDomains
 
implement main
    open syntaxDomains
 
clauses
    run() :-
        Tree1 = tree([]),
        Tree2 = tree([]),
        _Result = toBoolean(Tree1 = Tree2).
 
end implement main

I assume that your interface is not only parameterized because of these domains, so in a more realistic set up you can do like this:

Code: Select all

interface syntaxDomains{@Type}
 
domains
    tree{T} = tree(subTree{T}* SubTreeList).
    subTree{T} =
        leaf(T Value);
        branch(tree{T} Tree).
 
domains
    treeT = tree{@Type}.
    
predicates
    p : (treeT Tree).
    q : (tree{@Type} Tree).
 
end interface syntaxDomains

p and q has the same type.

The main thing is that the recursive domains does not reference the type parameter of the scope (i.e. @Type), but only uses local type parameters.

The non-recursive treeT domain can reference @Type without problems.

Martin Meyer · Post by **Martin Meyer** » 3 Oct 2016 0:15

Thank you Thomas!

I've changed my 'real' code in the way you advised, now it's working.

Best regards
Martin

Martin Meyer · Post by **Martin Meyer** » 18 May 2019 17:13

Hello Thomas,

I am bringing this issue back to the top because it (still or again) needs a treatment (in build 902).

Post by **Thomas Linder Puls** » 18 May 2019 21:57

Thank you, we will look at it.

Re: Problem with Comparing Trees

Re: Problem with Comparing Trees