Fix error in one dimensional MC integration

Also:
- fixes uninitialized sum
- removes unreferenced variables

Resolves #438

Author: hollasch

CHANGELOG.md

@@ -17,6 +17,11 @@ Change Log -- Ray Tracing in One Weekend
 - Fix: Introduce `u`,`v` surface coordinates to `hit_record` (#441)
 - Fix: Add highlight to new `hittable::bounding_box()` method (#442)
 
+### _The Rest of Your Life_
+- Fix: unitialized variable in first version of `integrate_x_sq.cc`
+- Fix: remove unreferenced variables in several sample programs
+- Fix: correct program computation of the integral of x^2 (#438)
+
 
 ----------------------------------------------------------------------------------------------------
 # v3.0.1 (2020-03-31)

books/RayTracingTheRestOfYourLife.html

@@ -221,16 +221,14 @@
     #include <stdlib.h>
 
     int main() {
-        int inside_circle = 0;
-        int inside_circle_stratified = 0;
         int N = 1000000;
-        double sum;
+        auto sum = 0.0;
         for (int i = 0; i < N; i++) {
             auto x = random_double(0,2);
             sum += x*x;
         }
         std::cout << std::fixed << std::setprecision(12);
-        std::cout << "I = " << sum/N << '\n';
+        std::cout << "I = " << 2 * sum/N << '\n';
     }
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     [Listing [integ-xsq-1]: <kbd>[integrate_x_sq.cc]</kbd> Integrating $x^2$]
@@ -406,8 +404,6 @@
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
 
     int main() {
-        int inside_circle = 0;
-        int inside_circle_stratified = 0;
         int N = 1000000;
         auto sum = 0.0;
         for (int i = 0; i < N; i++) {
@@ -439,8 +435,6 @@
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
 
     int main() {
-        int inside_circle = 0;
-        int inside_circle_stratified = 0;
         int N = 1000000;
         auto sum = 0.0;
         for (int i = 0; i < N; i++) {
@@ -484,8 +478,6 @@
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
 
     int main() {
-        int inside_circle = 0;
-        int inside_circle_stratified = 0;
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
         int N = 1;
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++