proposition: Lemma eq_in_dlet f g mu nu : {in dinsupp mu, f =2 g} -> mu =1 nu -> dlet f mu =1 dlet g nu.
proof: Proof. move=> eq_f eq_mu; unlock dlet=> y /=; apply/eq_psum=> x. rewrite -eq_mu; case/boolP: (x \in dinsupp mu) => [/eq_f ->//|]. by move/dinsuppPn=> ->; rewrite !mul0r. Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.classical(boolp classical_sets mathcomp_extra) xfinmap ereal reals discrete topology realseq realsum