From d38e9a82b7bdff9f990ff5c5650366890f16cfe8 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 30 Oct 2015 21:50:32 -0700
Subject: Define suspend operator.

* lisplib.c (yield_set_entries): Added "suspend" to
end of name.

* share/txr/stdlib/yield.tl (suspend): New macro.

* txr.1: Documented suspend. Replaced subtly incorect
shift/reset implementation example with suspend implementation.
---
 share/txr/stdlib/yield.tl | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'share')

diff --git a/share/txr/stdlib/yield.tl b/share/txr/stdlib/yield.tl
index 236faaa8..3b58ace2 100644
--- a/share/txr/stdlib/yield.tl
+++ b/share/txr/stdlib/yield.tl
@@ -64,3 +64,11 @@
 
 (defmacro yield (form)
   ^(yield-from nil ,form))
+
+(defmacro suspend (:form form name var . body)
+  (with-gensyms (cap val)
+    ^(tree-bind (,cap . ,val) (sys:capture-cont ',name ',form)
+       (if ,cap
+         (let ((,var ,val))
+           (sys:abscond-from ,name ,*body))
+         ,val))))
-- 
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