example: Explain new SBF-related additions.

example/example.org

@@ -971,6 +971,54 @@ tab
    | 1 | 1 |  1 |  0 |
    :end:
 
+   =dds= also includes functions for dealing with SBF operating on
+   states.  In particular, to create an SBF, you can do:
+
+   #+BEGIN_SRC racket :results output drawer
+(make-sbf/state '((a . -1) (b . 1)))
+   #+END_SRC
+
+   #+RESULTS:
+   :results:
+   (tbf/state '#hash((a . -1) (b . 1)) 0)
+   :end:
+
+   Most of the functions operating on TBF can be directly applied to
+   SBF and therefore have no specialization for this particular case.
+   However, there are variants of reading and printing functions for
+   SBF.
+
+   Consider the following table giving the weights of two SBF:
+
+   #+NAME: simple-sbfs/state
+   |  a | b |
+   |  1 | 1 |
+   | -2 | 1 |
+
+   You can read these SBFs in the following way:
+
+   #+BEGIN_SRC racket :results output drawer :var simple-sbfs/state=munch-sexp(simple-sbfs/state)
+(read-org-sbfs/state simple-sbfs/state)
+   #+END_SRC
+
+   #+RESULTS:
+   :results:
+   (list (tbf/state '#hash((a . 1) (b . 1)) 0) (tbf/state '#hash((a . -2) (b . 1)) 0))
+   :end:
+
+   You can print them back to an Org-mode table as follows:
+
+   #+BEGIN_SRC racket :results table drawer :var simple-sbfs/state=munch-sexp(simple-sbfs/state)
+(print-org-sbfs/state (read-org-sbfs/state simple-sbfs/state))
+   #+END_SRC
+
+   #+RESULTS:
+   :results:
+   |  a | b |
+   |  1 | 1 |
+   | -2 | 1 |
+   :end:
+
 * Reaction systems
   :PROPERTIES:
   :header-args:racket: :prologue "#lang racket\n(require graph dds/rs dds/utils)"