Adding promisep function.

* eval.c (promisep): New static function.
(eval_init): Registered promisep intrinsic.

* txr.1: Documented promisep.

1 files changed, 21 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index 6e612436..9b6d6490 100644
--- a/txr.1
+++ b/txr.1
@@ -15624,6 +15624,27 @@ the promise will take on the value of
 .meta expression
 or the assigned value.
 
+.coNP Function @ promisep
+.synb
+.mets (promisep << object )
+.syne
+.desc
+The
+.code promisep
+function returns
+.code t
+if
+.meta object
+is a promise object: an object created by the
+.code delay
+macro.  Otherwise it returns
+.codn nil .
+
+Note: promise objects are conses. The
+.code typeof
+function applied to a promise returns
+.codn cons .
+
 .coNP Macro @ mlet
 .synb
 .mets (mlet >> ({ sym | >> ( sym << init-form )}*) << body-form *)