better structure, format and docs

misc/cartesian_to_polar.c

@@ -3,39 +3,48 @@
  * @brief Function to convert a Cartesian co-ordinate to polar form.
  */
 #define _USE_MATH_DEFINES /**< required for MS Visual C */
+#include <assert.h>
 #include <math.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 /**
-give as arguments to the executable two x and y coordinates
-outputs a polar coordinate
-*/
-int main()
+ * @brief Function to convert cartesian coordinates to polar.
+ *\f{eqnarray*}{
+ r &=& \sqrt{x^2+y^2}\\
+ \theta &=& \atan\frac{y}{x}
+ \f}
+ * @param [in] x absicca value
+ * @param [in] y ordinate value
+ * @param [out] r pointer to store polar radius
+ * @param [out] theta pointer to store polar angle (in radian)
+ */
+void to_polar(double x, double y, double *r, double *theta)
 {
-    double x, y;
-    double r, theta, thetaFinal;
-    scanf("%lf %lf", &x, &y);
-    r = hypot(x, y);
+    double thetaFinal;
+
+    *r = sqrt(x * x + y * y);
+
     if (x != 0)
     {
         if (y != 0)
         {
-            theta = atan(y / x);
+            *theta = atan(y / x);
             if ((x > 0 && y > 0) || (x == -y))
             {  // Q1
-                thetaFinal = theta;
+                thetaFinal = *theta;
             }
             else if (x < 0 && y > 0)
             {  // Q2
-                thetaFinal = theta + M_PI;
+                thetaFinal = *theta + M_PI;
             }
             else if (x < 0 && y < 0)
             {  // Q3
-                thetaFinal = theta - M_PI;
+                thetaFinal = *theta - M_PI;
             }
             else if (x > 0 && y < 0)
             {  // Q4
-                thetaFinal = 2 * M_PI - theta;
+                thetaFinal = 2 * M_PI - *theta;
             }
         }
     }
@@ -61,5 +70,50 @@ int main()
             thetaFinal = -M_PI;
         }
     }
-    printf("%.2f %.2f\n", r, atan2(y, x));
+
+    *theta = thetaFinal;
+}
+
+/**
+ * @brief Generate a random number in the given limits
+ *
+ * @param lim1 lower limit
+ * @param lim2 upper limit
+ * @return random number in the given range
+ */
+double get_rand(double lim1, double lim2)
+{
+    double r = (double)rand() / RAND_MAX;  // value in [0,1)
+    return (lim2 - lim1) * r + lim1;       // scale to range
+}
+
+/**
+ * @brief Test implementation
+ *
+ */
+void test()
+{
+    srand(10);
+    int NUM_TESTS = 5;
+
+    for (int i = 0; i < NUM_TESTS; i++)
+    {
+        double r, theta;
+        printf("Test %d.... ", i);
+        double x = get_rand(-5, 5);
+        double y = get_rand(-5, 5);
+        printf("(%.2g, %.2g).... ", x, y);
+        to_polar(x, y, &r, &theta);
+        assert(fabs(r - hypot(x, y)) < 0.01);
+        assert(fabs(theta - atan2(y, x)) < 0.01);
+        printf("passed\n");
+    }
+}
+
+/** Main function */
+int main()
+{
+    test();
+
+    return 0;
 }