1. 24 Mar, 2017 2 commits
    • Robbert Krebbers's avatar
      Make big_opL type class opaque. · 02a0929d
      Robbert Krebbers authored
      This commit fixes the issues that refolding of big operators did not work nicely
      in the proof mode, e.g., given:
          Goal forall M (P : nat → uPred M) l,
            ([∗ list] x ∈ 10 :: l, P x) -∗ True.
          Proof. iIntros (M P l) "[H1 H2]".
      We got:
          "H1" : P 10
          "H2" : (fix
                  big_opL (M0 : ofeT) (o : M0 → M0 → M0) (H : Monoid o) (A : Type)
                          (f : nat → A → M0) (xs : list A) {struct xs} : M0 :=
                    match xs with
                    | [] => monoid_unit
                    | x :: xs0 => o (f 0 x) (big_opL M0 o H A (λ n : nat, f (S n)) xs0)
                    end) (uPredC M) uPred_sep uPred.uPred_sep_monoid nat
                   (λ _ x : nat, P x) l
      The problem here is that proof mode looked for an instance of `IntoAnd` for
      `[∗ list] x ∈ 10 :: l, P x` and then applies the instance for separating conjunction
      without folding back the fixpoint. This problem is not specific to the Iris ...
    • Robbert Krebbers's avatar
      Generic big operators that are no longer tied to CMRAs. · 6fbff46e
      Robbert Krebbers authored
      Instead, I have introduced a type class `Monoid` that is used by the big operators:
          Class Monoid {M : ofeT} (o : M → M → M) := {
            monoid_unit : M;
            monoid_ne : NonExpansive2 o;
            monoid_assoc : Assoc (≡) o;
            monoid_comm : Comm (≡) o;
            monoid_left_id : LeftId (≡) monoid_unit o;
            monoid_right_id : RightId (≡) monoid_unit o;
      Note that the operation is an argument because we want to have multiple monoids over
      the same type (for example, on `uPred`s we have monoids for `∗`, `∧`, and `∨`). However,
      we do bundle the unit because:
      - If we would not, the unit would appear explicitly in an implicit argument of the
        big operators, which confuses rewrite. By bundling the unit in the `Monoid` class
        it is hidden, and hence rewrite won't even see it.
      - The unit is unique.
      We could in principle have big ops over setoids instead of OFEs. However, since we do
      not have a canonical structure for bundled setoids, I did not go that way.