Adding a tagbody macro to the language.

This is a "disciplined goto" feature of Common Lisp.
This uses a new sys:switch operator, which could
also be used for optimizing case and cond forms.

* eval.c (switch_s): New symbol variable.
(op_switch, expand_list_of_form_lists, expand_switch):
New static functions.
(do_expand): Hook in the expansion of the sys:switch
operator.
(eval_init): Initialize switch_s special variable to
sys:switch symbol. Register sys:switch special op.

* lisplib.c (tagbody_set_entries, tagbody_instantiate): New
static functions.
(lisplib_init): Register autoloading of tagbody module
via new functions.

* share/txr/stdlib/tagbody.tl: New file.

* txr.1: Documented.

1 files changed, 17 insertions, 0 deletions

diff --git a/lisplib.c b/lisplib.c
index 713bb480..d1f237c4 100644
--- a/lisplib.c
+++ b/lisplib.c
@@ -446,6 +446,22 @@ static val getput_instantiate(val set_fun)
   return nil;
 }
 
+static val tagbody_set_entries(val dlt, val fun)
+{
+  val name[] = {
+    lit("tagbody"), lit("go"), nil
+  };
+  set_dlt_entries(dlt, name, fun);
+  return nil;
+}
+
+static val tagbody_instantiate(val set_fun)
+{
+  funcall1(set_fun, nil);
+  load(format(nil, lit("~atagbody.tl"), stdlib_path, nao));
+  return nil;
+}
+
 val dlt_register(val dlt,
                  val (*instantiate)(val),
                  val (*set_entries)(val, val))
@@ -481,6 +497,7 @@ void lisplib_init(void)
   dlt_register(dl_table, getopts_instantiate, getopts_set_entries);
   dlt_register(dl_table, package_instantiate, package_set_entries);
   dlt_register(dl_table, getput_instantiate, getput_set_entries);
+  dlt_register(dl_table, tagbody_instantiate, tagbody_set_entries);
 }
 
 val lisplib_try_load(val sym)