org: examples with alternating automata

* doc/org/tut23.org, doc/org/tut24.org, doc/org/tut31.org: New files.
* doc/Makefile.am, doc/org/tut.org: Add them.
* doc/org/hoa.org, doc/org/concepts.org: Adjust for alternation support.
* NEWS: Add links.

doc/org/tut31.org

@@ -0,0 +1,173 @@
+# -*- coding: utf-8 -*-
+#+TITLE: Alternation removal
+#+DESCRIPTION: Code example for removing alternation in Spot
+#+SETUPFILE: setup.org
+#+HTML_LINK_UP: tut.html
+
+Consider the following alternating co-Büchi automaton (see [[file:tut23.org][how to
+create it]]):
+
+#+NAME: tut31in
+#+BEGIN_SRC hoa
+HOA: v1
+States: 3
+Start: 0
+AP: 1 "a"
+acc-name: co-Buchi
+Acceptance: 1 Fin(0)
+properties: univ-branch trans-labels explicit-labels trans-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[0] 0
+[!0] 0&1
+State: 1
+[!0] 1 {0}
+[0] 2
+State: 2
+[t] 2
+--END--
+#+END_SRC
+
+#+NAME: tut31dot
+#+BEGIN_SRC sh :results verbatim :exports none :noweb strip-export
+cat >tut31.hoa <<EOF
+<<tut31in>>
+EOF
+autfilt --dot=.a tut31.hoa
+#+END_SRC
+
+#+BEGIN_SRC dot :file tut31in.png :cmdline -Tpng :var txt=tut31dot :exports results
+  $txt
+#+END_SRC
+
+#+RESULTS:
+[[file:tut31in.png]]
+
+Our goal is to transform this alternating automaton into a
+non-alternating automaton.
+
+Alternation support in Spot should be considered as experimental.
+Currently, alternation removal is only supported for weak alternating
+automata, i.e., SCCs should have all there transitions in the same
+acceptance marks.  The =remove_alternation()= procedure of Spot will
+produce a [[file:concepts.org::#trans-acc][TGBA]] for [[file:concepts.org::#property-flags][weak]] input, but the smallest automata are obtained
+if the input is [[file:concepts.org::#property-flags][very-weak]].
+
+* Shell
+
+We simply use =autfilt= with option =--tgba=:
+
+#+BEGIN_SRC sh :results verbatim :exports both :wrap SRC hoa
+autfilt --tgba tut31.hoa
+#+END_SRC
+#+RESULTS:
+#+BEGIN_SRC hoa
+HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels trans-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[!0] 0 {0}
+[0] 1 {0}
+State: 1
+[0] 1 {0}
+[!0] 1
+--END--
+#+END_SRC
+
+#+NAME: tut31out
+#+BEGIN_SRC sh :results verbatim :exports none
+autfilt --tgba -d tut31.hoa
+#+END_SRC
+
+#+BEGIN_SRC dot :file tut31out.png :cmdline -Tpng :var txt=tut31out :exports results
+$txt
+#+END_SRC
+
+#+RESULTS:
+[[file:tut31out.png]]
+
+* Python
+
+In the Python version we call =remove_alternation()=
+
+#+BEGIN_SRC python :results output :exports both :wrap SRC hoa
+import spot
+aut = spot.remove_alternation(spot.automaton('tut31.hoa'))
+print(aut.to_str('hoa'))
+#+END_SRC
+#+RESULTS:
+#+BEGIN_SRC hoa
+HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels trans-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[0] 0 {0}
+[!0] 1 {0}
+State: 1
+[0] 0 {0}
+[!0] 1
+--END--
+#+END_SRC
+
+* C++
+
+The C++ version calls =remove_alternation()= too.
+
+#+BEGIN_SRC C++ :results verbatim :exports both :wrap SRC hoa
+  #include <iostream>
+  #include <spot/parseaut/public.hh>
+  #include <spot/twaalgos/alternation.hh>
+  #include <spot/twaalgos/hoa.hh>
+
+  int main()
+  {
+    spot::parsed_aut_ptr pa = parse_aut("tut31.hoa", spot::make_bdd_dict());
+    if (pa->format_errors(std::cerr))
+      return 1;
+    if (pa->aborted)
+      {
+        std::cerr << "--ABORT-- read\n";
+        return 1;
+      }
+    auto aut = spot::remove_alternation(pa->aut);
+    spot::print_hoa(std::cout, aut) << '\n';
+    return 0;
+  }
+#+END_SRC
+
+#+RESULTS:
+#+BEGIN_SRC hoa
+HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels trans-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[0] 0 {0}
+[!0] 1 {0}
+State: 1
+[0] 0 {0}
+[!0] 1
+--END--
+#+END_SRC
+
+#+BEGIN_SRC sh :results silent :exports results
+rm -f tut31.hoa
+#+END_SRC