Chapter 8 correction for problemm 3

thinkcspy/Chapter-8-Exercises/Exercises.md

@@ -25,10 +25,6 @@ So that's when `bound` was created. Problem was, I initialized it to the value o
 That was a pretty fun problem! Alright, now to the solution:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 2
-
 def print_triangular_numbers(n):
     # your code here
     i = 1
@@ -65,10 +61,6 @@ Now the real struggle was working with primes larger than 2. Turns out that solu
 But then we get back to the whole “taking too many steps thing”. I did more research and learned that taking the square root of `n` and making that the limit for the while loop would help the program execute a lot faster than testing if x was greater than. Then I reinitialized x to 3, incremented it by 2 instead of decrementing it by 2 and wallah! I had a program that was decently efficient and effective and it passed all the built in tests!
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 3
-
 import math
 
 def is_prime(n):
@@ -93,6 +85,50 @@ print(is_prime(4813))
 
 ![](Exercises/1_image.png)
 
+### Correction (Oct 15, 2023):
+
+While learning about loops and arrays in JavaScript, I had a similar problem where I had to print all the prime numbers for a given number. I came back to this one as a reference and realized that there was actually an issue with the way I looked for prime numbers. For some reason, the number 25 returned `True`, when it should have returned `False`.
+
+ This is how I solved the problem in JavaScript:
+
+```application-javascript-env-frontend
+let n = prompt("Enter a positive integer.");
+
+outer: 
+for (let i = 2; i <= n; i++){
+  
+  for (let j = 2; j < i; j++){
+    if (i % j == 0) continue outer;
+  }
+
+  console.log(i);    
+}
+```
+
+Result with an input of 25:
+
+![](Exercises/8_image.png)
+
+With the above script as a reference, this is how I revised my solution for problem 3:
+
+```text-x-python
+def is_prime(n):
+    # your code 
+        
+    for i in range (2, n):
+        if n % i == 0:
+            return False
+    return True
+
+print(is_prime(25))
+```
+
+Result:
+
+![](Exercises/7_image.png)
+
+Once again, the built in tests are not the end all be all for these problems (see chapter 9's exercises for more context). I passed the tests with the last iteration of my problem, but there was still that _one_ number (25 and maybe more), that got missed by the tests. 
+
 Turtle Problems
 ---------------
 
@@ -113,10 +149,6 @@ I'm combining problems 4 through 6 because they build on each other.
 ### Initial code from an earlier lesson section:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Section 4 
-
 import random
 import turtle
 
@@ -155,13 +187,9 @@ wn.exitonclick()
 
 ### My Code
 
-Oh boy.. this section was a lot. Problem 4 was pretty easy, though. All I had to do was have them go at a random angle. That initial code looked like this:
+Oh boy.. this one was a lot. Problem 4 was pretty easy. All I had to do was have them go at a random angle. That initial code looked like this:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 4
-
 import random
 import turtle
 
@@ -201,10 +229,6 @@ wn.exitonclick()
 The random starting position proved to be more challenging. The calculations were all fine from the getgo. The issue was I forgot bring the pen up before I moved the turtles to a random location. I ended up moving on to the image problems before coming back to this and realizing that lol. Here's the code for that:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 5
-
 import random
 import turtle
 
@@ -293,10 +317,6 @@ I also changed the angle from `180` to `170` and that seemed to keep the turtles
 Here's the final code:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 6
-
 import random
 import turtle
 import math
@@ -388,8 +408,7 @@ wn.exitonclick()
 
 Result:
 
-I started recording after the turtles already got moving, but you get the idea. 
-
+I started after the turtles already got moving, but you get the idea. 
 ![](Exercises/turtlemoves-2023-09-29_11.47.3.gif)
 
 Image problems
@@ -400,10 +419,6 @@ The following problems used the following image and code (from an earlier lesson
 ![](Exercises/LutherBellPic.jpg)
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Section 11 
-
 import image
 
 img = image.Image("luther.jpg")
@@ -434,10 +449,6 @@ win.exitonclick()
 This was my initial solution. 
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 8
-
 import image
 
 img = image.Image("luther.jpg")
@@ -465,15 +476,11 @@ And the result:
 
 ![](Exercises/3_image.png)
 
-But then I had to figure out turning that into a function. I was going to go the lazy route and leave it as it was since it gave me the solution I was looking for, but then I figured actually turning this into a function would help me with the next problem. 
+But then I had to figure out turning That into a function. I was going to go the lazy route and leave it as it was since it gave me the solution I was looking for, but then I figured actually turning this into a function would help me with the next problem. 
 
 Here was my final solution with the function:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 8
-
 import image
 
 def greyScale (red, blue, green):    
@@ -511,10 +518,6 @@ And the result, of course, is the same:
 This was my initial solution:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 9
-
 import image
 
 img = image.Image("luther.jpg")
@@ -551,10 +554,6 @@ The result was:
 Close, but not quite. I needed black and white, not high contrast. But my intuition was in the ballpark. I figured that this would work better if I actually took the solution I got from the grey scale problem and then turned _that_ black and white. So, I went back to Problem 8, turned my solution into a function and then fixed up the code for this problem like this:
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 9
-
 import image
 
 def greyScale (red, blue, green):
@@ -604,10 +603,6 @@ win.exitonclick()
 This didn't take too much effort since they gave me the formula. Just sharing, because I think it's cool.
 
 ```text-x-python
-# Runestone.Academy thinkcspy course
-# Chapter 8
-# Problem 10
-
 import image