===================================================================
RCS file: /cvs/mandoc/roff.7,v
retrieving revision 1.89
retrieving revision 1.91
diff -u -p -r1.89 -r1.91
--- mandoc/roff.7	2017/06/14 13:00:31	1.89
+++ mandoc/roff.7	2017/06/14 19:39:18	1.91
@@ -1,4 +1,4 @@
-.\"	$Id: roff.7,v 1.89 2017/06/14 13:00:31 schwarze Exp $
+.\"	$Id: roff.7,v 1.91 2017/06/14 19:39:18 schwarze Exp $
 .\"
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2010,2011,2013-2015,2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -412,7 +412,6 @@ Create an alias for a number register.
 Currently unsupported.
 .It Ic \&als Ar newname oldname
 Create an alias for a request, string, macro, or diversion.
-Currently unsupported.
 .It Ic \&am Ar macroname Op Ar endmacro
 Append to a macro definition.
 The syntax of this request is the same as that of
@@ -1045,8 +1044,6 @@ If the first character of
 is
 .Sq c
 .Pq character available ,
-.Sq d
-.Pq string defined ,
 .Sq e
 .Pq even page ,
 .Sq t
@@ -1055,6 +1052,15 @@ or
 .Sq v
 .Pq vroff mode ,
 it evaluates to false.
+.It
+If the first character of
+.Ar condition
+is
+.Sq d ,
+it evaluates to true if the rest of
+.Ar condition
+is the name of an existing user defined macro or string;
+otherwise, it evaluates to false.
 .It
 If the first character of
 .Ar condition