Factored distance calculation into separate utility class

Makefile

@@ -4,7 +4,7 @@ PROJECT=graphgame
 CXX=g++
 CXXFLAGS=-DDEBUG -g
 LDFLAGS=-lSDL
-OBJECTS=drawutils.o gamecore.o graph.o main.o mainevent.o
+OBJECTS=drawutils.o gamecore.o graph.o main.o mainevent.o mathutils.o
 
 all: $(PROJECT)
 

drawutils.cpp

@@ -1,5 +1,6 @@
 #include "drawutils.h"
 #include <cmath>
+#include "mathutils.h"
 
 SDL_Surface* DrawUtils::load(string file)
 {
@@ -58,15 +59,12 @@ void DrawUtils::draw_line(SDL_Surface* dest, Sint16 x1, Sint16 y1, Sint16 x2, Si
 
     SDL_Rect pen;
 
-    dx = static_cast<float>(x2-x1);
+    len = MathUtils::distance(x1,y1,x2,y2);
-    dy = static_cast<float>(y2-y1);
-
-    len = sqrt(dx*dx + dy*dy);
 
     // changing dx and dy's meanings. Now they represent the amount we move
     // each step in our drawing loop
-    dx /= len;
+    dx = static_cast<float>(x2-x1) / len;
-    dy /= len;
+    dy = static_cast<float>(y2-y1) / len;
 
     int j = static_cast<int>(len);
 

graph.cpp

@@ -1,8 +1,6 @@
 #include "graph.h"
 #include "debug.h"
-#include <cmath>
+#include "mathutils.h"
-
-using std::abs;
 
 int Graph::MAX_MOVE_DISTANCE = 100;
 
@@ -77,7 +75,11 @@ void Graph::select_vertex(int x, int y)
 void Graph::add_vertex(int x, int y, int size)
 {
     if (current_vertex != NULL &&
-	(Vertex::distance(*current_vertex, Vertex(x, y)) > MAX_MOVE_DISTANCE))
+	(MathUtils::distance(static_cast<float>(current_vertex->x),
+			     static_cast<float>(current_vertex->y),
+			     static_cast<float>(x),
+			     static_cast<float>(y))
+	 > MAX_MOVE_DISTANCE))
 	return;
 
     Vertex* v = new Vertex(x, y);
@@ -102,11 +104,3 @@ void Graph::add_vertex(int x, int y, int size)
     edges.push_back(e);
     current_vertex = v;
 }
-
-
-float Vertex::distance(Vertex a, Vertex b)
-{
-    float dy = abs(static_cast<float>(b.y) - a.y);
-    float dx = abs(static_cast<float>(b.x) - a.x);
-    return sqrt(dy*dy + dx*dx);
-}

graph.h

@@ -20,11 +20,9 @@ class Vertex
     int x;
     int y;
     int x_min;
-    int x_max;
     int y_min;
+    int x_max;
     int y_max;
-
-    static float distance(Vertex a, Vertex b);
 };
 
 struct Edge

mathutils.cpp

@@ -0,0 +1,9 @@
+#include "mathutils.h"
+#include <math.h>
+
+float MathUtils::distance(float x1, float y1, float x2, float y2)
+{
+    float dy = y2 - y1;
+    float dx = x2 - x1;
+    return sqrt(dy*dy + dx*dx);
+}

mathutils.h

@@ -0,0 +1,14 @@
+/* Some handy mathematics utilities
+ */
+
+#ifndef _MATHUTILS_H_
+#define _MATHUTILS_H_
+
+class MathUtils
+{
+ public:
+    // returns the cartesian distance of two points
+    static float distance(float x1, float y1, float x2, float y2);
+};
+
+#endif