How to transfer a binary variable into a continuous variable in OPL Script?

Question

I have a binary decision variable X and I need to convert it into a continuous variable so it can take continuous values between 0 and 1 (i.e. 0.3). I need to learn how to change a decision variable type in the OPL script part.

Answer 1

See example

//Now let's see how easy it is to relax integrity constraints and
//turn a MIP into LP, solve and get dual value (shadow price)

int nbKids=300;
float costBus40=500;
float costBus30=400;
 
dvar int+ nbBus40;
dvar int+ nbBus30;
 
minimize
 costBus40*nbBus40  +nbBus30*costBus30;
 
subject to
{
 ctKids:40*nbBus40+nbBus30*30>=nbKids;
}
main {
  var status = 0;
  thisOplModel.generate();
  if (cplex.solve()) {
    writeln("Integer Model");   
    writeln("OBJECTIVE: ",cplex.getObjValue());   
    
  }
  // relax integrity constraint
  thisOplModel.convertAllIntVars();
 
  if (cplex.solve()) {
    writeln("Relaxed Model");   
    writeln("OBJECTIVE: ",cplex.getObjValue());  
    
    writeln("dual of the kids constraint = ",thisOplModel.ctKids.dual);
  }
   
 
}