Real variables (constraints)

[FAMILIAR-project]

The current strategy is to "emulate" real (double) with integer with ad-hoc management of precision...
Basically we multiply the double by the precision needed (10, 100, ...) and then convert back the values (solution) by dividing.

FeatureModelVariable fmv = FM("VARY_LATEX : [SUBTITLE] FIGURE_TUX ACK LONG_AFFILIATION; ACK : (MOREACK|BOLDACK); LONG_AFFILIATION : [EMAIL]  ; ");
      fmv.setFeatureAttribute(fmv.getFeature("FIGURE_TUX"), "vspace_tux", new IntegerDomainVariable("", 5, 10)); // TODO: type the attribute
      fmv.setFeatureAttribute(fmv.getFeature("FIGURE_TUX"), "size_tux", new DoubleDomainVariable("", 3.0, 5.0, 100.0)); // TODO: type the attribute
      Collection<AttributedConstraintVariable> cstsAtts = new HashSet<>();
      cstsAtts.add(new AttributedConstraintVariable(new AttributedExpression("vspace_tux", ArithmeticCompOperator.GE, 7)));
      cstsAtts.add(new AttributedConstraintVariable(new AttributedExpression("size_tux", ArithmeticCompOperator.GE, 4.9)));

It works pretty well.
The problem I am seeing is when you want to constrain two real variables that have not the same precision

 fmv.setFeatureAttribute(fmv.getFeature("FIGURE_TUX"), "size_tux", new DoubleDomainVariable("", 3.0, 5.0, 100.0)); // TODO: type the attribute
 fmv.setFeatureAttribute(fmv.getFeature("FIGURE_TUX"), "size_tux2", new DoubleDomainVariable("", 3.0, 5.0, 10.0)); // TODO: type the attribute
cstsAtts.add(new AttributedConstraintVariable(new AttributedExpression("size_tux", ArithmeticCompOperator.GE, "size_tux2")));

In such cases, you will compare 30 with 300 :(
So an idea is to have a fixed precision for all double variables.

We have to be careful with constraints between integers and doubles