expander: support param macros in nested macro param lists.

Parameter list macros work in inside macro parameter lists,
like they do in function parameter lists. However, they
ony work at the top level. Macro parameter lists are nested;
they may contain nested parameter lists that match
corresponding shapes in the argument list.
This patch extends parameter list macros to work in
nested macro parameter lists.

* eval.c (expand_opt_params_rec, expand_params_rec):
These two functions must be extended to take a body
argument, and to return not just an expanded parameter
list but a parameter list accompanied by a body.
We do that by making them return a cons cell, whose
car is the expanded parameter list and the cdr is
the possibly transformed body. Additionally, these
functions now call expand_param_macro on nested
macro parameter lists.
(expand_params): This function becomes slightly simpler
as a result of the above changes. Because expand_params_rec
already returns a cons cell holding a parameter list and
body, we just return that as-is.

* tests/011/keyparams.tl: Added some tests of this, vie the
standard :key parameter list macro. A macro is tested
which has a nested (:key ...) parameter list in a required
parameter position as well as in an optional position.

* txr.1: Documented.

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/011/keyparams.tl b/tests/011/keyparams.tl
index e2f8baf2..189081d3 100644
--- a/tests/011/keyparams.tl
+++ b/tests/011/keyparams.tl
@@ -2,6 +2,8 @@
 
 (defvarl v :v)
 (defsymacro u (identity :u))
+(defvarl x :x)
+(defvarl y :y)
 
 (mtest
   [(lambda (:key))] nil
@@ -36,3 +38,10 @@
 
 (test
   (set (key-place :x 3 :y 4) 42) (3 4 42 t))
+
+(defmacro kp (r (:key -- (a v a-p) (b u b-p)) : ((:key -- (c x c-p) (d y d-p))))
+  ^'(r ,a ,a-p ,b ,b-p ,c ,c-p ,d ,d-p))
+
+(mtest
+  (kp :r ()) (r :v nil :u nil :x nil :y nil)
+  (kp 0 (:a 1 :b 2) (:d 3)) (r 1 t 2 t :x nil 3 t))