Abstract evaluation
<n(incr(incr(new(C)))),{ C }> -[new]->
<n(incr(incr(C))),{ C[n:=0] }> -[incr]->
<n(incr(C)),{ C[n:=1] }> -[incr]->
<n(C), { C[n:=2] }> -[n]->
<2, { C[n:=2] }>
<n(incr(incr(new(C)))),{ C }> -[new]->
<n(incr(incr(C))),{ C[n:=0] }> -[incr]->
<n(incr(C)),{ C[n:=1] }> -[incr]->
<n(C), { C[n:=2] }> -[n]->
<2, { C[n:=2] }>