Fixes small AC malus of less than 1 resulting in a bonus of 1 AC

Source/items.cpp

@@ -16,6 +16,7 @@
 #include "options.h"
 #include "stores.h"
 #include "utils/language.h"
+#include "utils/math.h"
 
 namespace devilution {
 
@@ -600,7 +601,7 @@ void CalcPlrItemVals(int p, bool Loadgfx)
 					tmpac *= itm->_iPLAC;
 					tmpac /= 100;
 					if (tmpac == 0)
-						tmpac = 1;
+						tmpac = math::Sign(itm->_iPLAC);
 					bac += tmpac;
 				}
 				iflgs |= itm->_iFlags;

Source/utils/math.h

@@ -0,0 +1,24 @@
+/**
+* @file math.h
+*
+* Math utility functions
+*/
+#pragma once
+
+namespace devilution {
+namespace math {
+
+/**
+ * @brief Compute sign of t
+ * @tparam T Any arithmetic type
+ * @param t Value to compute sign of
+ * @return -1 if t < 0, 1 if t > 0, 0 if t == 0
+*/
+template<typename T>
+int Sign(T t)
+{
+	return (t > T(0)) - (t < T(0));
+}
+
+} // namespace math
+} // namespace devilution