Support keyword params via :key param list macro.

* eval.c (expand_param_macro): Use lisplib_try_load to retry
failed parameter macro lookup, thereby supporting auto-loading
of modules that define parameter macros.

* lisplib.c (keyparams_set_entries, keyparams_instantiate): New static
functions.
(lisplib_init): Support autoloading of keyparams.tl via new
functions.

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

* txr.1: Documented :key param list macro.

* checkman.txr: Support "Parameter list macro" documentation
section type.

1 files changed, 7 insertions, 3 deletions

diff --git a/eval.c b/eval.c
index 015ee9af..fed5c7ed 100644
--- a/eval.c
+++ b/eval.c
@@ -941,9 +941,13 @@ static val expand_param_macro(val params, val body, val menv, val form)
         sym == env_k ||sym == colon_k)
       return cons(params, body);
 
-    if (!pmac)
-      eval_error(form, lit("~s: keyword ~s has no param macro binding"),
-                 car(form), sym, nao);
+    if (!pmac) {
+      lisplib_try_load(sym);
+      pmac = gethash(pm_table, sym);
+      if (!pmac)
+        eval_error(form, lit("~s: keyword ~s has no param macro binding"),
+                   car(form), sym, nao);
+    }
 
     {
       val prest = cdr(params);