From 2e96e2cab74d00b40188b00a4e90eeeaa1c46706 Mon Sep 17 00:00:00 2001
From: Andres Erbsen <andreser@mit.edu>
Date: Sat, 25 Jun 2016 15:08:21 -0400
Subject: EdDSA: prove things about spec

---
 src/Util/Option.v | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 src/Util/Option.v

(limited to 'src/Util/Option.v')

diff --git a/src/Util/Option.v b/src/Util/Option.v
new file mode 100644
index 000000000..db4b69dde
--- /dev/null
+++ b/src/Util/Option.v
@@ -0,0 +1,62 @@
+Require Import Coq.Classes.Morphisms.
+
+Global Instance option_rect_Proper_nd {A T}
+  : Proper ((pointwise_relation _ eq) ==> eq  ==> eq ==> eq) (@option_rect A (fun _ => T)).
+Proof.
+  intros ?? H ??? [|]??; subst; simpl; congruence.
+Qed.
+
+Global Instance option_rect_Proper_nd' {A T}
+  : Proper ((pointwise_relation _ eq) ==> eq  ==> forall_relation (fun _ => eq)) (@option_rect A (fun _ => T)).
+Proof.
+  intros ?? H ??? [|]; subst; simpl; congruence.
+Qed.
+
+Hint Extern 1 (Proper _ (@option_rect ?A (fun _ => ?T))) => exact (@option_rect_Proper_nd' A T) : typeclass_instances.
+
+Lemma option_rect_option_map : forall {A B C} (f:A->B) some none v,
+    option_rect (fun _ => C) (fun x => some (f x)) none v = option_rect (fun _ => C) some none (option_map f v).
+Proof.
+  destruct v; reflexivity.
+Qed.
+
+Lemma option_rect_function {A B C S' N' v} f
+  : f (option_rect (fun _ : option A => option B) S' N' v)
+    = option_rect (fun _ : option A => C) (fun x => f (S' x)) (f N') v.
+Proof. destruct v; reflexivity. Qed.
+
+(*
+Ltac commute_option_rect_Let_In := (* pull let binders out side of option_rect pattern matching *)
+  idtac;
+  lazymatch goal with
+  | [ |- ?LHS = option_rect ?P ?S ?N (Let_In ?x ?f) ]
+    => (* we want to just do a [change] here, but unification is stupid, so we have to tell it what to unfold in what order *)
+    cut (LHS = Let_In x (fun y => option_rect P S N (f y))); cbv beta;
+    [ set_evars;
+      let H := fresh in
+      intro H;
+      rewrite H;
+      clear;
+      abstract (cbv [Let_In]; reflexivity)
+    | ]
+  end.
+*)
+
+(** TODO: possibly move me, remove local *)
+Ltac replace_option_match_with_option_rect :=
+  idtac;
+  lazymatch goal with
+  | [ |- _ = ?RHS :> ?T ]
+    => lazymatch RHS with
+       | match ?a with None => ?N | Some x => @?S x end
+         => replace RHS with (option_rect (fun _ => T) S N a) by (destruct a; reflexivity)
+       end
+  end.
+
+Ltac simpl_option_rect := (* deal with [option_rect _ _ _ None] and [option_rect _ _ _ (Some _)] *)
+  repeat match goal with
+         | [ |- context[option_rect ?P ?S ?N None] ]
+           => change (option_rect P S N None) with N
+         | [ |- context[option_rect ?P ?S ?N (Some ?x) ] ]
+           => change (option_rect P S N (Some x)) with (S x); cbv beta
+         end.
-- 
cgit v1.2.3