+/// Score struct keeps a midgame and an endgame value in a single
+/// ScoreValue 64 bit union.
+
+enum Score;
+
+inline Value eg_value(Score s) { return Value(int16_t(s & 0xffff)); }
+inline Value mg_value(Score s) { return Value((int(s) + 32768) >> 16); }
+
+inline Score make_score(int mg, int eg) { return Score((mg << 16) + eg); }
+
+inline Score operator-(Score s) { return Score(-int(s)); }
+inline Score operator+(Score s1, Score s2) { return Score(int(s1) + int(s2)); }
+inline Score operator-(Score s1, Score s2) { return Score(int(s1) - int(s2)); }
+inline void operator+=(Score& s1, Score s2) { s1 = Score(int(s1) + int(s2)); }
+inline void operator-=(Score& s1, Score s2) { s1 = Score(int(s1) - int(s2)); }
+inline Score operator*(int i, Score s) { return Score(i * int(s)); }
+
+// Division must be handled separately for each term
+inline Score operator/(Score s, int i) { return make_score(mg_value(s) / i, eg_value(s) / i); }
+
+// Only declared but not defined. We don't want to multiply two scores due to
+// a very high risk of overflow. So user should explicitly convert to integer.
+inline Score operator*(Score s1, Score s2);
+
+