let c = {c with grefs = succ c.grefs} in
let c = {c with pars = c.pars + List.length ts} in
let c = {c with xnodes = succ c.xnodes + List.length ts} in
let c = {c with grefs = succ c.grefs} in
let c = {c with pars = c.pars + List.length ts} in
let c = {c with xnodes = succ c.xnodes + List.length ts} in