Add basics/util.hh

A place for NearZero, etc

src/basics/util.hh

@@ -0,0 +1,61 @@
+/* util.hh
+ * vim: set tw=80:
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+#ifndef __BASICS_UTIL_HH__
+#define __BASICS_UTIL_HH__
+
+#include <cmath>
+
+
+/**
+ * A very small constant. If a value is between EPSILON and 0.0, it is
+ * considered to be zero.
+ */
+const Double EPSILON = 1.0e-10;
+
+
+/**
+ * The maximum distance a ray can travel. This is the maximum value t can be.
+ */
+const Double MAX_DISTANCE = 1.0e7;
+
+
+/**
+ * Determine if the value is "close enough" to zero. Takes the absolute value
+ * and compares it to `EPSILON`.
+ *
+ * @see EPSILON
+ *
+ * @param [in] value    The value to check
+ * @returns `true` if the value is close enough to zero
+ */
+template <typename T>
+inline bool
+NearZero(T value)
+{
+    return std::fabs(value) < EPSILON;
+}
+
+
+/**
+ * Determine if two values are "close enough" to be considered equal. Subtracts
+ * one from the other and checks if the result is near zero.
+ *
+ * @see NearZero
+ *
+ * @param [in] left     The left parameter
+ * @param [in] right    The right parameter
+ * @returns `true` if the values are close enough to be equal
+ */
+template <typename T, typename U>
+inline bool
+NearlyEqual(T left,
+            U right)
+{
+    return NearZero(left - right);
+}
+
+#endif /* __BASICS_UTIL_HH__ */
+