[gecode-users] Generating constraints

[Max]

I have no problem in writing a tree analyzer but i looked for a uniform 
representation of the variables, operators, relations and constants, so 
i do not have to write an extra function for all of them.
I want to write

recursive_function_call rfc(X):
IntVar temp;
//switch for operator
add(rfc(x1), ADD, rfc(x2), temp);
return temp;

I don't want to distinguish the leafs of the node at this step. So i 
need a uniform return value.
PS: Does it influence the performance if i use temporary variables for 
my constants.

IntVar x(this, 5,5);




Mikael Zayenz Lagerkvist wrote:
> Hi,
>
> If you have a tree representing an expression, then you should write a
> tree-analyzer (a tree-walker for example) that posts constraints that
> correspond to the tree. This is how the linear expressions in Gecodes
> MiniModel works. For more information on writing tree analyzers, see a
> compiler text as it corresponds to instruction selection.
>
> There is no way to undo a tell - you have to copy the space.
>
> Cheers,
> Mikael
>
>
> On Tue, Oct 28, 2008 at 12:58 PM, Max <chaosangel at gmx.de> wrote:
>   
>> Hello all,
>>
>> i currently try to post constraints and need your help.
>> I have my constraints not in a textual format, but in a self made tree
>> structure of the form
>>
>>
>>                              rel">="
>>                             /         \
>>                           op+      const=5
>>                        /       \
>>                var=x       const=7
>>
>>
>> (i hope this is readable)
>>
>> Now i want to generate and post a gecode constraint of it.
>> Is there an easy way to recursivly define a constraint, because it seems
>> to me that there is no baseclass or something that can be used.
>>
>> I wanted to to something of the form
>>
>> GeCodeConstraint recursive_converter(MyConstraint)
>> {
>>       if "variable" return x;
>>       if "constant" return 5;
>>       if "op+" return recursive_converter(left_node) +
>> recursive_converter(right_node);
>>       if "rel>=" return recursive_converter(left_node) >=
>> recursive_converter(right_node);
>> }
>>
>>
>> I i found for GeCodeConstraint was MiniModel::LinRel<>, is there
>> something more uniform, because i want to use boolean and integer
>> variables (reified constraints) and stuff.
>> (the arithmetic functions seem very generic returning a variable, but
>> then a lot of extra variables would have to be generated)
>>
>>
>> Any ideas ?
>>
>> 2nd question:
>>
>> Is there a way to post the value of a variable not in form of a
>> constraint, so "branch" on a boolean variable but being able to undo it so
>>
>> so
>> b[0].set(0);
>> //after some time
>> b[0].set(1);
>>
>> without copying the whole space?
>>
>> Thank you a lot.
>>
>> Max
>>
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>>
>>     
>
>
>
>