From 398fcda3ac71e99fb3bdd5c3d1fa69099c50fdb4 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Mon, 13 Mar 2017 06:41:26 -0700
Subject: Add in-package directive.

* match.c (in_package_s): New symbol variable.
(syms_init): Initialize in_package_s.

* match.h (in_package_s): Declared.

* parser.y (check_parse_time_action): Add case for in-package.
Evaluate just with eval, as a case of the in-package macro.

* txr.1: Documented.
---
 match.c  |  3 ++-
 match.h  |  2 +-
 parser.y |  4 ++++
 txr.1    | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/match.c b/match.c
index 60b5a6df..6fda6f19 100644
--- a/match.c
+++ b/match.c
@@ -60,7 +60,7 @@ val mingap_k, maxgap_k, gap_k, mintimes_k, maxtimes_k, times_k;
 val lines_k, chars_k;
 val text_s, choose_s, gather_s, do_s, mdo_s, mod_s, modlast_s;
 val line_s, data_s, fuzz_s, load_s;
-val include_s, close_s, require_s;
+val include_s, close_s, require_s, in_package_s;
 val longest_k, shortest_k, greedy_k;
 val vars_k, resolve_k;
 val append_k, into_k, var_k, list_k, tlist_k, string_k, env_k, counter_k;
@@ -4689,6 +4689,7 @@ static void syms_init(void)
   include_s = intern(lit("include"), user_package);
   close_s = intern(lit("close"), user_package);
   require_s = intern(lit("require"), user_package);
+  in_package_s = intern(lit("in-package"), user_package);
   longest_k = intern(lit("longest"), keyword_package);
   shortest_k = intern(lit("shortest"), keyword_package);
   greedy_k = intern(lit("greedy"), keyword_package);
diff --git a/match.h b/match.h
index 9894ecff..35e7cd05 100644
--- a/match.h
+++ b/match.h
@@ -25,7 +25,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-extern val text_s, choose_s, gather_s, do_s, mdo_s, require_s;
+extern val text_s, choose_s, gather_s, do_s, mdo_s, require_s, in_package_s;
 extern val close_s, load_s, include_s, mod_s, modlast_s, line_s;
 extern val counter_k, vars_k, env_k, var_k, into_k, named_k;
 val match_expand_keyword_args(val elem);
diff --git a/parser.y b/parser.y
index 6615a3e7..9f628227 100644
--- a/parser.y
+++ b/parser.y
@@ -1676,6 +1676,10 @@ static val check_parse_time_action(val spec_rev)
         eval_intrinsic(cons(progn_s, cdr(elem)), nil);
         return nil;
       }
+      if (sym == in_package_s) {
+        eval_intrinsic(elem, nil);
+        return nil;
+      }
     }
   }
   return spec_rev;
diff --git a/txr.1 b/txr.1
index 50bb99c2..98c0f37b 100644
--- a/txr.1
+++ b/txr.1
@@ -3276,6 +3276,12 @@ The
 directive evaluates \*(TL expressions immediately, during the parsing
 of the \*(TX syntax in which it occurs.
 
+.coIP @(in-package)
+The
+.code in-package
+directive is used to switch to a different symbol package.
+It mirrors the \*(TL macro of the same name.
+
 .PP
 
 .SS* Subexpression Evaluation
@@ -6580,6 +6586,34 @@ can be used as a horizontal or vertical directive, whereas
 .code mdo
 is only vertical.
 
+.dir in-package
+
+The
+.code in-package
+directive shares the same syntax and semantics as the \*(TL macro
+of the same name:
+
+.cblk
+.mets (in-package << name )
+.cble
+
+The
+.code in-package
+directive is evaluated immediately upon being parsed,
+leaving no trace in the syntax tree of the surrounding \*(TX
+query.
+
+It causes the
+.code *package*
+special variable to take on the package denoted by
+.metn name .
+
+The directive that
+.meta name
+is either a string or symbol. An error exception is thrown if
+this isn't the case.  Otherwise it searches for the package.
+If the package is not found, an error exception is thrown.
+
 .SS* Blocks
 
 .NP* Overview
-- 
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