feat(library/tactic): add 'change' tactic

hott/init/tactic.hlean

@@ -92,6 +92,9 @@ notation `clears` `(` l:(foldr `,` (h t, expr_list.cons h t) expr_list.nil) `)`
 opaque definition revert_lst (ids : expr_list) : tactic := builtin
 notation `reverts` `(` l:(foldr `,` (h t, expr_list.cons h t) expr_list.nil) `)` := revert_lst l
 
+opaque definition change_goal (e : expr) : tactic := builtin
+notation `change` e := change_goal e
+
 opaque definition assert_hypothesis (id : expr) (e : expr) : tactic := builtin
 
 infixl `;`:15 := and_then

library/init/tactic.lean

@@ -91,6 +91,9 @@ notation `clears` `(` l:(foldr `,` (h t, expr_list.cons h t) expr_list.nil) `)`
 opaque definition revert_lst (ids : expr_list) : tactic := builtin
 notation `reverts` `(` l:(foldr `,` (h t, expr_list.cons h t) expr_list.nil) `)` := revert_lst l
 
+opaque definition change_goal (e : expr) : tactic := builtin
+notation `change` e := change_goal e
+
 opaque definition assert_hypothesis (id : expr) (e : expr) : tactic := builtin
 
 infixl `;`:15 := and_then

src/emacs/lean-syntax.el

@@ -131,7 +131,7 @@
             (or "\\b.*_tac" "Cond" "or_else" "then" "try" "when" "assumption" "eassumption" "rapply"
                 "apply" "fapply" "rename" "intro" "intros"
                 "generalize" "generalizes" "clear" "clears" "revert" "reverts" "back" "beta" "done" "exact" "repeat"
-                "whnf" "rotate" "rotate_left" "rotate_right" "inversion" "cases" "rewrite" "esimp" "unfold"))
+                "whnf" "rotate" "rotate_left" "rotate_right" "inversion" "cases" "rewrite" "esimp" "unfold" "change"))
            word-end)
       (1 'font-lock-constant-face))
      ;; Types

src/library/constants.cpp

@@ -69,6 +69,8 @@ name const * g_tactic_assumption = nullptr;
 name const * g_tactic_at_most = nullptr;
 name const * g_tactic_beta = nullptr;
 name const * g_tactic_builtin = nullptr;
+name const * g_tactic_change_goal = nullptr;
+name const * g_tactic_change_hypothesis = nullptr;
 name const * g_tactic_clear = nullptr;
 name const * g_tactic_clear_lst = nullptr;
 name const * g_tactic_determ = nullptr;
@@ -178,6 +180,8 @@ void initialize_constants() {
     g_tactic_at_most = new name{"tactic", "at_most"};
     g_tactic_beta = new name{"tactic", "beta"};
     g_tactic_builtin = new name{"tactic", "builtin"};
+    g_tactic_change_goal = new name{"tactic", "change_goal"};
+    g_tactic_change_hypothesis = new name{"tactic", "change_hypothesis"};
     g_tactic_clear = new name{"tactic", "clear"};
     g_tactic_clear_lst = new name{"tactic", "clear_lst"};
     g_tactic_determ = new name{"tactic", "determ"};
@@ -288,6 +292,8 @@ void finalize_constants() {
     delete g_tactic_at_most;
     delete g_tactic_beta;
     delete g_tactic_builtin;
+    delete g_tactic_change_goal;
+    delete g_tactic_change_hypothesis;
     delete g_tactic_clear;
     delete g_tactic_clear_lst;
     delete g_tactic_determ;
@@ -397,6 +403,8 @@ name const & get_tactic_assumption_name() { return *g_tactic_assumption; }
 name const & get_tactic_at_most_name() { return *g_tactic_at_most; }
 name const & get_tactic_beta_name() { return *g_tactic_beta; }
 name const & get_tactic_builtin_name() { return *g_tactic_builtin; }
+name const & get_tactic_change_goal_name() { return *g_tactic_change_goal; }
+name const & get_tactic_change_hypothesis_name() { return *g_tactic_change_hypothesis; }
 name const & get_tactic_clear_name() { return *g_tactic_clear; }
 name const & get_tactic_clear_lst_name() { return *g_tactic_clear_lst; }
 name const & get_tactic_determ_name() { return *g_tactic_determ; }

src/library/constants.h

@@ -71,6 +71,8 @@ name const & get_tactic_assumption_name();
 name const & get_tactic_at_most_name();
 name const & get_tactic_beta_name();
 name const & get_tactic_builtin_name();
+name const & get_tactic_change_goal_name();
+name const & get_tactic_change_hypothesis_name();
 name const & get_tactic_clear_name();
 name const & get_tactic_clear_lst_name();
 name const & get_tactic_determ_name();

src/library/constants.txt

@@ -64,6 +64,8 @@ tactic.assumption
 tactic.at_most
 tactic.beta
 tactic.builtin
+tactic.change_goal
+tactic.change_hypothesis
 tactic.clear
 tactic.clear_lst
 tactic.determ

src/library/tactic/CMakeLists.txt

@@ -3,6 +3,7 @@ apply_tactic.cpp intros_tactic.cpp rename_tactic.cpp trace_tactic.cpp
 exact_tactic.cpp unfold_tactic.cpp generalize_tactic.cpp
 inversion_tactic.cpp whnf_tactic.cpp revert_tactic.cpp
 assert_tactic.cpp clear_tactic.cpp expr_to_tactic.cpp location.cpp
-rewrite_tactic.cpp util.cpp class_instance_synth.cpp init_module.cpp)
+rewrite_tactic.cpp util.cpp class_instance_synth.cpp init_module.cpp
+change_tactic.cpp)
 
 target_link_libraries(tactic ${LEAN_LIBS})

src/library/tactic/change_tactic.cpp

@@ -0,0 +1,56 @@
+/*
+Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#include "library/constants.h"
+#include "kernel/type_checker.h"
+#include "library/reducible.h"
+#include "library/tactic/tactic.h"
+#include "library/tactic/elaborate.h"
+#include "library/tactic/expr_to_tactic.h"
+
+namespace lean {
+tactic change_goal_tactic(elaborate_fn const & elab, expr const & e) {
+    return tactic01([=](environment const & env, io_state const & ios, proof_state const & s) {
+            proof_state new_s = s;
+            goals const & gs  = new_s.get_goals();
+            if (!gs) {
+                throw_no_goal_if_enabled(s);
+                return none_proof_state();
+            }
+            expr t            = head(gs).get_type();
+            bool report_unassigned = true;
+            if (auto new_e = elaborate_with_respect_to(env, ios, elab, new_s, e, none_expr(), report_unassigned)) {
+                goals const & gs    = new_s.get_goals();
+                goal const & g      = head(gs);
+                name_generator ngen = new_s.get_ngen();
+                substitution subst  = new_s.get_subst();
+                auto tc             = mk_type_checker(env, ngen.mk_child());
+                constraint_seq cs;
+                if (tc->is_def_eq(t, *new_e, justification(), cs) && !cs) {
+                    expr M   = g.mk_meta(ngen.next(), *new_e);
+                    goal new_g(M, *new_e);
+                    expr val = g.abstract(M);
+                    subst.assign(g.get_name(), val);
+                    return some(proof_state(new_s, cons(new_g, tail(gs)), subst, ngen));
+                } else {
+                    // generate error
+                    return none_proof_state();
+                }
+            }
+            return none_proof_state();
+        });
+}
+
+void initialize_change_tactic() {
+    register_tac(get_tactic_change_goal_name(),
+                 [](type_checker &, elaborate_fn const & fn, expr const & e, pos_info_provider const *) {
+                     check_tactic_expr(app_arg(e), "invalid 'change' tactic, invalid argument");
+                     return change_goal_tactic(fn, get_tactic_expr_expr(app_arg(e)));
+                 });
+}
+void finalize_change_tactic() {
+}
+}

src/library/tactic/change_tactic.h

@@ -0,0 +1,13 @@
+/*
+Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#pragma once
+#include "library/tactic/tactic.h"
+
+namespace lean {
+void initialize_change_tactic();
+void finalize_change_tactic();
+}

src/library/tactic/init_module.cpp

@@ -21,6 +21,7 @@ Author: Leonardo de Moura
 #include "library/tactic/assert_tactic.h"
 #include "library/tactic/class_instance_synth.h"
 #include "library/tactic/rewrite_tactic.h"
+#include "library/tactic/change_tactic.h"
 
 namespace lean {
 void initialize_tactic_module() {
@@ -41,9 +42,11 @@ void initialize_tactic_module() {
     initialize_assert_tactic();
     initialize_class_instance_elaborator();
     initialize_rewrite_tactic();
+    initialize_change_tactic();
 }
 
 void finalize_tactic_module() {
+    finalize_change_tactic();
     finalize_rewrite_tactic();
     finalize_class_instance_elaborator();
     finalize_assert_tactic();