From 5aa6b0a6b2ac0561125716710662adab6ad6f333 Mon Sep 17 00:00:00 2001
From: Jason Gross <jgross@mit.edu>
Date: Sat, 8 Jul 2017 15:59:53 -0400
Subject: Add UnfoldArg

---
 _CoqProject                    |  1 +
 src/Util/Tactics.v             |  1 +
 src/Util/Tactics/ChangeInAll.v |  4 ++++
 src/Util/Tactics/UnfoldArg.v   | 11 +++++++++++
 4 files changed, 17 insertions(+)
 create mode 100644 src/Util/Tactics/UnfoldArg.v

diff --git a/_CoqProject b/_CoqProject
index aadb4a93d..430e377a6 100644
--- a/_CoqProject
+++ b/_CoqProject
@@ -357,6 +357,7 @@ src/Util/Tactics/SubstEvars.v
 src/Util/Tactics/SubstLet.v
 src/Util/Tactics/Test.v
 src/Util/Tactics/TransparentAssert.v
+src/Util/Tactics/UnfoldArg.v
 src/Util/Tactics/UnifyAbstractReflexivity.v
 src/Util/Tactics/UniquePose.v
 src/Util/Tactics/VM.v
diff --git a/src/Util/Tactics.v b/src/Util/Tactics.v
index 4d39d4954..af75b4f50 100644
--- a/src/Util/Tactics.v
+++ b/src/Util/Tactics.v
@@ -35,6 +35,7 @@ Require Export Crypto.Util.Tactics.SubstEvars.
 Require Export Crypto.Util.Tactics.SubstLet.
 Require Export Crypto.Util.Tactics.Test.
 Require Export Crypto.Util.Tactics.TransparentAssert.
+Require Export Crypto.Util.Tactics.UnfoldArg.
 Require Export Crypto.Util.Tactics.UnifyAbstractReflexivity.
 Require Export Crypto.Util.Tactics.UniquePose.
 Require Export Crypto.Util.Tactics.VM.
diff --git a/src/Util/Tactics/ChangeInAll.v b/src/Util/Tactics/ChangeInAll.v
index 39a031207..c18055962 100644
--- a/src/Util/Tactics/ChangeInAll.v
+++ b/src/Util/Tactics/ChangeInAll.v
@@ -5,3 +5,7 @@ Ltac change_in_all from to :=
   repeat match goal with
          | [ H : _ |- _ ] => progress change from with to in H
          end.
+
+Ltac change_with_compute_in_all c :=
+  let c' := (eval compute in c) in
+  change c with c' in *.
diff --git a/src/Util/Tactics/UnfoldArg.v b/src/Util/Tactics/UnfoldArg.v
new file mode 100644
index 000000000..5f7772578
--- /dev/null
+++ b/src/Util/Tactics/UnfoldArg.v
@@ -0,0 +1,11 @@
+Require Import Crypto.Util.Tactics.ChangeInAll.
+
+(** fully reduces the first argument to [t], wherever it appears *)
+Ltac unfold_first_arg t :=
+  repeat match goal with
+         | [ H : context[t ?x] |- _ ] => progress change_with_compute_in_all x
+         | [ |- context[t ?x] ] => progress change_with_compute_in_all x
+         end.
+
+(* use uconstr so we can have underscores *)
+Tactic Notation "unfold_first_arg" uconstr(t) := unfold_first_arg t.
-- 
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