geom/segment: add normalised and unnormalised direction queries

geom/segment.hpp

@@ -64,6 +64,25 @@ namespace cruft::geom {
     }
 
 
+    /// Returns the un-normalised direction of the segment from its start to
+    /// end components. ie, `a' to `b'.
+    template <size_t S, typename T>
+    cruft::vector<S,T>
+    udirection (segment<S,T> const &val)
+    {
+        return val.b - val.a;
+    }
+
+
+    /// Returns the normalised direction of the segment.
+    template <size_t S, typename T>
+    cruft::vector<S,T>
+    ndirection (segment<S,T> const &val)
+    {
+        return normalised (udirection (val));
+    }
+
+
     using segment2i = segment<2,int>;
     using segment3i = segment<3,int>;