1 files changed, 61 insertions, 0 deletions
diff --git a/gi/posterior-regularisation/alphabet.hh b/gi/posterior-regularisation/alphabet.hh
new file mode 100644
index 00000000..1db928da
--- /dev/null
+++ b/gi/posterior-regularisation/alphabet.hh
@@ -0,0 +1,61 @@
+#ifndef _alphabet_hh
+#define _alphabet_hh
+
+#include <cassert>
+#include <iosfwd>
+#include <map>
+#include <string>
+#include <vector>
+
+// Alphabet: indexes a set of types 
+template <typename T>
+class Alphabet: protected std::map<T, int>
+{
+public:
+    Alphabet() {};
+
+    bool empty() const { return std::map<T,int>::empty(); }
+    int size() const { return std::map<T,int>::size(); }
+
+    int operator[](const T &k) const
+    {
+        typename std::map<T,int>::const_iterator cit = find(k);
+        if (cit != std::map<T,int>::end())
+            return cit->second;
+        else
+            return -1;
+    }
+
+    int lookup(const T &k) const { return (*this)[k]; }
+
+    int insert(const T &k) 
+    {
+        int sz = size();
+        assert((unsigned) sz == _items.size());
+
+        std::pair<typename std::map<T,int>::iterator, bool>
+            ins = std::map<T,int>::insert(make_pair(k, sz));
+
+        if (ins.second) 
+            _items.push_back(k);
+
+        return ins.first->second;
+    }
+
+    const T &type(int i) const
+    {
+        assert(i >= 0);
+        assert(i < size());
+        return _items[i];
+    }
+
+    std::ostream &display(std::ostream &out, int i) const
+    {
+        return out << type(i);
+    }
+
+private:
+    std::vector<T> _items;
+};
+
+#endif