acc: add support for generating parity conditions

* src/twa/acc.cc, src/twa/acc.hh: Here.
* wrap/python/tests/accparse.ipynb: Test it.

src/twa/acc.cc

@@ -445,6 +445,32 @@ namespace spot
     return true;
   }
 
+  acc_cond::acc_code
+  acc_cond::acc_code::parity(bool max, bool odd, unsigned sets)
+  {
+    if (sets == 0)
+      return f();
+    // When you look at something like
+    //    acc-name: parity min even 5
+    //    Acceptance: 5 Inf(0) | (Fin(1) & (Inf(2) | (Fin(3) & Inf(4))))
+    // remember that we build it from right to left.
+    int start = max ? 0 : sets - 1;
+    int inc = max ? 1 : -1;
+    int end = max ? sets : -1;
+    // Do not start with a Fin term, the right-most term is always Inf.
+    if ((start & 1) != odd)
+      start += inc;
+    acc_cond::acc_code res = f();
+    for (int i = start; i != end; i += inc)
+      {
+	if ((i & 1) == odd)
+	  res.append_or(inf({(unsigned)i}));
+	else
+	  res.append_and(fin({(unsigned)i}));
+      }
+    return res;
+  }
+
   namespace
   {
     bdd to_bdd_rec(const acc_cond::acc_word* c, const bdd* map)
@@ -1186,6 +1212,44 @@ namespace spot
       return res;
     }
 
+    static bool max_or_min(const char*& input)
+    {
+      skip_space(input);
+      if (!strncmp(input, "max", 3))
+	{
+	  input += 3;
+	  return true;
+	}
+      if (!strncmp(input, "min", 3))
+	{
+	  input += 3;
+	  return false;
+	}
+      std::ostringstream s;
+      s << "syntax error at '" << input
+	<< "': expecting 'min' or 'max'";
+      throw parse_error(s.str());
+    }
+
+    static bool odd_or_even(const char*& input)
+    {
+      skip_space(input);
+      if (!strncmp(input, "odd", 3))
+	{
+	  input += 3;
+	  return true;
+	}
+      if (!strncmp(input, "even", 4))
+	{
+	  input += 4;
+	  return false;
+	}
+      std::ostringstream s;
+      s << "syntax error at '" << input
+	<< "': expecting 'odd' or 'even'";
+      throw parse_error(s.str());
+    }
+
   }
 
   acc_cond::acc_code parse_acc_code(const char* input)
@@ -1245,6 +1309,14 @@ namespace spot
 	  }
 	c = acc_cond::acc_code::generalized_rabin(v.begin(), v.end());
       }
+    else if (!strncmp(input, "parity", 6))
+      {
+	input += 6;
+	bool max = max_or_min(input);
+	bool odd = odd_or_even(input);
+	unsigned num = parse_num(input);
+	c = acc_cond::acc_code::parity(max, odd, num);
+      }
     else
       {
 	c = parse_acc(input);

src/twa/acc.hh

@@ -519,6 +519,8 @@ namespace spot
 	return res;
       }
 
+      static acc_code parity(bool max, bool odd, unsigned sets);
+
       void append_and(acc_code&& r)
       {
 	if (is_true() || r.is_false())

wrap/python/tests/accparse.ipynb

@@ -105,7 +105,13 @@
       "            'co-Buchi', 'generalized-co-Buchi 3', 'generalized-co-Buchi 0',\n",
       "            'Rabin 2', 'Rabin 0',\n",
       "            'Streett 2', 'Streett 0',\n",
-      "            'generalized-Rabin 3 1 2 3', 'generalized-Rabin 0']:\n",
+      "            'generalized-Rabin 3 1 2 3', 'generalized-Rabin 0',\n",
+      "            'parity min even 6', 'parity max odd 6', 'parity max even 6', 'parity min odd 6',\n",
+      "            'parity min even 5', 'parity max odd 5', 'parity max even 5', 'parity min odd 5',\n",
+      "            'parity min even 2', 'parity max odd 2', 'parity max even 2', 'parity min odd 2',\n",
+      "            'parity min even 1', 'parity max odd 1', 'parity max even 1', 'parity min odd 1',\n",
+      "            'parity min even 0', 'parity max odd 0', 'parity max even 0', 'parity min odd 0',\n",
+      "            ]:\n",
       "    print(acc, ': ', spot.parse_acc_code(acc), sep='')"
      ],
      "language": "python",
@@ -128,20 +134,31 @@
         "Streett 2: (Fin(0) | Inf(1)) & (Fin(2) | Inf(3))\n",
         "Streett 0: t\n",
         "generalized-Rabin 3 1 2 3: (Fin(0) & Inf(1)) | (Fin(2) & (Inf(3)&Inf(4))) | (Fin(5) & (Inf(6)&Inf(7)&Inf(8)))\n",
-        "generalized-Rabin 0: f\n"
+        "generalized-Rabin 0: f\n",
+        "parity min even 6: Inf(0) | (Fin(1) & (Inf(2) | (Fin(3) & Inf(4))))\n",
+        "parity max odd 6: Inf(5) | (Fin(4) & (Inf(3) | (Fin(2) & Inf(1))))\n",
+        "parity max even 6: Fin(5) & (Inf(4) | (Fin(3) & (Inf(2) | (Fin(1) & Inf(0)))))\n",
+        "parity min odd 6: Fin(0) & (Inf(1) | (Fin(2) & (Inf(3) | (Fin(4) & Inf(5)))))\n",
+        "parity min even 5: Inf(0) | (Fin(1) & (Inf(2) | (Fin(3) & Inf(4))))\n",
+        "parity max odd 5: Fin(4) & (Inf(3) | (Fin(2) & Inf(1)))\n",
+        "parity max even 5: Inf(4) | (Fin(3) & (Inf(2) | (Fin(1) & Inf(0))))\n",
+        "parity min odd 5: Fin(0) & (Inf(1) | (Fin(2) & Inf(3)))\n",
+        "parity min even 2: Inf(0)\n",
+        "parity max odd 2: Inf(1)\n",
+        "parity max even 2: Fin(1) & Inf(0)\n",
+        "parity min odd 2: Fin(0) & Inf(1)\n",
+        "parity min even 1: Inf(0)\n",
+        "parity max odd 1: f\n",
+        "parity max even 1: Inf(0)\n",
+        "parity min odd 1: f\n",
+        "parity min even 0: f\n",
+        "parity max odd 0: f\n",
+        "parity max even 0: f\n",
+        "parity min odd 0: f\n"
        ]
       }
      ],
      "prompt_number": 5
-    },
-    {
-     "cell_type": "code",
-     "collapsed": true,
-     "input": [],
-     "language": "python",
-     "metadata": {},
-     "outputs": [],
-     "prompt_number": null
     }
    ],
    "metadata": {}