restructured library manual accordiung to functional group
diff --git a/Doc/libarray.tex b/Doc/libarray.tex
index 9e37d55..8122f49 100644
--- a/Doc/libarray.tex
+++ b/Doc/libarray.tex
@@ -23,6 +23,9 @@
 architecture (strictly speaking, by the C implementation).  The actual
 size can be accessed through the \var{itemsize} attribute.
 
+See also built-in module \code{struct}.
+\bimodindex{struct}
+
 The module defines the following function:
 
 \renewcommand{\indexsubitem}{(in module array)}