proposition: Lemma indecomp_diff1 c a: indecomposable c -> a <o c -> c -o a = c.
proof: Proof. move =>ic [leac nac]. move: (odiff_pr leac)=> [od dv]. by case: (indecomp_pr (proj31 leac) od ic (esym dv)). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)