feat: add #[elem1, elem2, ..] notation for creating arrays

@kha @dselsam: I added this notation because I am tired of writing
`[elem1, elem2, ...].toArray`. BTW, the new notation is based on the
one available in SML.

src/frontends/lean/builtin_exprs.cpp

@@ -719,6 +719,11 @@ static expr parse_list(parser & p, unsigned, expr const *, pos_info const & pos)
     return r;
 }
 
+static expr parse_array(parser & p, unsigned n, expr const * l, pos_info const & pos) {
+    expr xs = parse_list(p, n, l, pos);
+    return p.save_pos(mk_app(mk_constant(get_list_to_array_name()), xs), pos);
+}
+
 static void consume_rparen(parser & p) {
     p.check_token_next(get_rparen_tk(), "invalid expression, `)` expected");
 }
@@ -819,6 +824,7 @@ parse_table init_nud_table() {
     r = r.add({transition("if", mk_ext_action(parse_if_then_else))}, x0);
     r = r.add({transition("(", mk_ext_action(parse_lparen))}, x0);
     r = r.add({transition("[", mk_ext_action(parse_list))}, x0);
+    r = r.add({transition("#[", mk_ext_action(parse_array))}, x0);
     r = r.add({transition("⟨", mk_ext_action(parse_constructor))}, x0);
     r = r.add({transition("{", mk_ext_action(parse_curly_bracket))}, x0);
     r = r.add({transition(".(", mk_ext_action(parse_inaccessible))}, x0);

src/frontends/lean/token_table.cpp

@@ -85,7 +85,7 @@ void init_token_table(token_table & t) {
          {"```(", g_max_prec}, {"`[", g_max_prec}, {"`", g_max_prec},
          {"%%", g_max_prec}, {"()", g_max_prec}, {"(::)", g_max_prec}, {")", 0}, {"'", 0},
          {"{", g_max_prec}, {"}", 0}, {"_", g_max_prec},
-         {"[", g_max_prec}, {"]", 0}, {"⦃", g_max_prec}, {"⦄", 0}, {".{", 0},
+         {"[", g_max_prec}, {"#[", g_max_prec}, {"]", 0}, {"⦃", g_max_prec}, {"⦄", 0}, {".{", 0},
          {"{!", g_max_prec}, {"!}", 0},
          {"Type", g_max_prec}, {"Type*", g_max_prec}, {"Sort", g_max_prec}, {"Sort*", g_max_prec},
          {"(:", g_max_prec}, {":)", 0}, {".(", g_max_prec}, {"._", g_max_prec},

src/library/constants.cpp

@@ -110,6 +110,7 @@ name const * g_lc_unreachable = nullptr;
 name const * g_list = nullptr;
 name const * g_list_nil = nullptr;
 name const * g_list_cons = nullptr;
+name const * g_list_to_array = nullptr;
 name const * g_match_failed = nullptr;
 name const * g_monad = nullptr;
 name const * g_monad_fail = nullptr;
@@ -295,6 +296,7 @@ void initialize_constants() {
     g_list = new name{"List"};
     g_list_nil = new name{"List", "nil"};
     g_list_cons = new name{"List", "cons"};
+    g_list_to_array = new name{"List", "toArray"};
     g_match_failed = new name{"matchFailed"};
     g_monad = new name{"Monad"};
     g_monad_fail = new name{"MonadFail"};
@@ -481,6 +483,7 @@ void finalize_constants() {
     delete g_list;
     delete g_list_nil;
     delete g_list_cons;
+    delete g_list_to_array;
     delete g_match_failed;
     delete g_monad;
     delete g_monad_fail;
@@ -666,6 +669,7 @@ name const & get_lc_unreachable_name() { return *g_lc_unreachable; }
 name const & get_list_name() { return *g_list; }
 name const & get_list_nil_name() { return *g_list_nil; }
 name const & get_list_cons_name() { return *g_list_cons; }
+name const & get_list_to_array_name() { return *g_list_to_array; }
 name const & get_match_failed_name() { return *g_match_failed; }
 name const & get_monad_name() { return *g_monad; }
 name const & get_monad_fail_name() { return *g_monad_fail; }

src/library/constants.h

@@ -112,6 +112,7 @@ name const & get_lc_unreachable_name();
 name const & get_list_name();
 name const & get_list_nil_name();
 name const & get_list_cons_name();
+name const & get_list_to_array_name();
 name const & get_match_failed_name();
 name const & get_monad_name();
 name const & get_monad_fail_name();

src/library/constants.txt

@@ -105,6 +105,7 @@ lcUnreachable
 List
 List.nil
 List.cons
+List.toArray
 matchFailed
 Monad
 MonadFail