Originally posted by: davidoff

In the following model, I try to build recursively the collection ypos.

I have the error

The collection "ypos" is immutable because it is referenced by another element.  
note that this error disappears if I set W to 27.

Any workaround for that problem ?

Thanks

David

int W=30;
{int} widths = { 9, 12};
int minWidth = min(w in widths) w;

sorted {int} ypos; 

//given widths w1, w2, ... , wN, , compute any integer combination sum(alpha_i*wi) <=  W -  minWidth
// a recursion is a natural way : given a new element, it will combine either alone or with all the previous combinations
execute ENUM_YPOS{
  function addNew(w){
    //1. recursion
    for(var y0 in ypos){
        var y=w;
        while(y+y0<=W-minWidth){
                ypos.add(y);
                y = y + w;
        }
    }      

   //2. add w alone
    var y=w;
    while(y<=W-minWidth){
        ypos.add(y);
        y = y + w;
    }   
        
   }
   
  for(var w in widths)
        addNew(w);
  ypos.add(0);  
}   
execute{
  writeln(ypos);
} 

Originally posted by: davidoff

All right, the error is in the loop from line 12, where we iterate on ypos and adding in ypos in the same time.

A solution is to store all ypos values in an intermediate collection, and then iterate on this collection to increment ypos

int W=30;
{int} widths = { 9, 12};
int minWidth = min(w in widths : w>0) w;


sorted {int} ypos; 
{int} tmp;
//given widths w1, w2, ... , wN, , compute any integer combination sum(alpha_i*wi) <=  W -  minWidth
// a recursion is a natural way : given a new element, it will combine either alone or with all the previous combinations
execute ENUM_YPOS{
  function addNew(w){
    //1. recursion
    writeln(Opl.card(tmp)," elems in tmp before");
    tmp.clear();
    writeln(Opl.card(tmp)," elems in tmp after");
    for(var y0 in ypos)
        tmp.add(y0);
    for(var y0 in tmp){
        var y=w;
        while(y+y0<=W-minWidth){
                ypos.add(y+y0);
                y = y + w;
        }
    }      

   //2. add w alone
    var y=w;
    while(y<=W-minWidth){
        ypos.add(y);
        y = y + w;
    }   
        
   }
   
  ypos.add(0);  
  for(var w in widths)
        addNew(w);
}  
 
execute{
  writeln("Finding all ypos with widths ",widths," and W=",W);
  writeln(ypos);
}