From 606e3e38b8a830dbbe65963ebf6c5ce7866b7800 Mon Sep 17 00:00:00 2001
From: Chris Dyer <redpony@gmail.com>
Date: Tue, 18 Mar 2014 01:41:17 -0400
Subject: star function

---
 utils/logval.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'utils/logval.h')

diff --git a/utils/logval.h b/utils/logval.h
index ec1f6acd..7f1e1024 100644
--- a/utils/logval.h
+++ b/utils/logval.h
@@ -11,6 +11,7 @@
 #include <cassert>
 #include "semiring.h"
 #include "show.h"
+#include "star.h"
 
 //TODO: template for supporting negation or not - most uses are for nonnegative "probs" only; probably some 10-20% speedup available
 template <class T>
@@ -242,4 +243,15 @@ bool operator>=(const LogVal<T>& lhs, const LogVal<T>& rhs) {
 template <class T>
 std::size_t hash_value(const LogVal<T>& x) { return x.hash_impl(); }
 
+template <class T>
+LogVal<T> star(LogVal<T> x) {
+  if (x.is_0()) return x;
+  if (x.v_ >= 0) {
+    x.v_ = std::numeric_limits<T>::infinity();
+  } else {
+    x.v_ = -log1p(-x.as_float());
+  }
+  return x;
+}
+
 #endif
-- 
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