matching.md in alf-0.10.1

- old
+ new

@@ -5,14 +5,18 @@
 
     #(signature)
 
 DESCRIPTION
 
-This operator restricts its LEFT operand to tuples for which there exists 
-at least one tuple in RIGHT that (naturally) joins. This is a shortcut 
-operator for the following longer expression:
+This operator restricts its LEFT operand to tuples for which there exists at 
+least one tuple in RIGHT that (naturally) joins. This is a shortcut operator 
+for the following longer expression:
 
     (project (join xxx, yyy), [xxx's attributes])
+
+Or equivalently,
+
+    (join xxx, (project xxx, [common attributes]))
 
 EXAMPLE
 
     # Which suppliers supply at least one part?
     !(alf matching suppliers supplies)