From 5d56b52e79d46adceeb672a68695a47d87106b8e Mon Sep 17 00:00:00 2001
From: David Kastrup <dak@gnu.org>
Date: Thu, 20 Oct 2011 18:49:13 +0200
Subject: [PATCH] Introduce void? predicate

---
 scm/c++.scm  | 3 +++
 scm/lily.scm | 1 +
 2 files changed, 4 insertions(+)

diff --git a/scm/c++.scm b/scm/c++.scm
index 74f58f4da3..915e7e6283 100644
--- a/scm/c++.scm
+++ b/scm/c++.scm
@@ -61,6 +61,9 @@
 (define-public (symbol-or-boolean? x)
   (or (symbol? x) (boolean? x)))
 
+(define-public (void? x)
+  (eq? x (begin)))
+
 ;; moved list to end of lily.scm: then all type-predicates are
 ;; defined.
 (define type-p-name-alist '())
diff --git a/scm/lily.scm b/scm/lily.scm
index 9157337ad1..88f1183b92 100644
--- a/scm/lily.scm
+++ b/scm/lily.scm
@@ -535,6 +535,7 @@ LilyPond safe mode.  The syntax is the same as `define*-public'."
     (,scheme? . "any type")
     (,string-or-pair? . "string or pair")
     (,string-or-symbol? . "string or symbol")
+    (,void? . "void")
     ))
 
 (define-public lilypond-exported-predicates
-- 
2.39.2