fact: Fixpoint filter_sum_left {A B} (l: list (A + B)) : list A := match l with | nil => nil | inl x :: l' => x :: filter_sum_left l' | inr _ :: l' => filter_sum_left l' end.
imports: Coq.Lists.List Coq.micromega.Lia Coq.Sorting.Permutation Coq.ZArith.ZArith_base Coq.ZArith.Zcomplements Coq.Logic.FunctionalExtensionality CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext VST.zlist.sublist VST.zlist.list_solver