variants compilation

doc/gf-history.html

@@ -25,6 +25,7 @@ weight random generation (<tt>gr -prob</tt>) and to rank parse
 results (<tt>p -prob</tt>). They are read from a separate file
 (flag <tt>i -probs=File</tt>, format <tt>--# prob Fun Double</tt>)
 or from the top-level grammar file itself (option <tt>i -prob</tt>).
+To see the probabilities, use <tt>pg -printer=probs</tt>.
 <br>
 As a by-product, the probabilistic random generation algorithm is
 available for any context-free abstract syntax. Use the flag