Riordina Lista bidirezionale

function riordina_bidir(l)
{
    var prev,cur,tmp={x:null,prec:null,succ:null};
    if(l==null){return;}
        else
        { prev=l;
            while(prev.prec!=null){prev=prev.prec;}
                while(prev!=null)
                {
                    for(cur=prev.succ;cur!=null;cur=cur.succ){
                        if(prev.x>cur.x){ tmp=pev.x;
                        prev.x=cur.x;cur.x=tmp;
                        }else{cur=cur.succ;}
                }
                    prev=prev.succ;}
        }
}