fact: Definition sum_until_none (xs : seq (option nat)) : contTi nat nat := callcc (fun break : nat -> contTi nat nat => foldM (break_if_none break) 0 xs).
imports: mathcomp(all_ssreflect) imonae_lib HB(structures) ihierarchy imonad_lib ifail_lib istate_lib itrace_lib imonad_transformer