+//if we modify the swag between calls, normal version may loop forever
+//this safe version ensures that we browse the swag elements only once
+lmm_variable_t lmm_get_var_from_cnst_safe(lmm_system_t /*sys*/,
+ lmm_constraint_t cnst,
+ lmm_element_t * elem,
+ lmm_element_t * nextelem,
+ int * numelem)
+{
+ if (!(*elem)){
+ *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->element_set));
+ *numelem = xbt_swag_size(&(cnst->element_set))-1;
+ }else{
+ *elem = *nextelem;
+ if(*numelem>0){
+ (*numelem) --;
+ }else
+ return NULL;
+ }
+ if (*elem){
+ *nextelem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->element_set.offset);
+ return (*elem)->variable;
+ }else
+ return NULL;
+}
+