CS 100 Spring 2014 Lab 4

Many Loops

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Using the Processing language/environment answer the following two questions.

1. [4 pts] Consider the following program that uses a while loop. Before running the program

1. trace the loop execution,
2. draw on a paper the coordinates that define each roof drawn and
3. determine how many roofs are drawn.

size(600,200);
background(240, 220, 120);

fill(220, 30, 30);
noStroke();

int roofHeight = 50;
int roofBaseY = 80;
int startX = 40;
int houseX = startX;
int houseSize = 100;
int houseDistance = houseSize + startX;

while(houseX+houseSize < width) {
   triangle(houseX, roofBaseY, 
            houseX+houseSize/2, roofBaseY-roofHeight, 
            houseX+houseSize, roofBaseY);
   houseX = houseX + houseDistance;
}
// reset the value of houseX
// houseX =

boolean boring = false;         
         
if (boring) {         
   fill(130, 130, 220);
} else
   fill(random(128, 255), random(128, 255), random(128, 255));
   
rect(houseX, roofBaseY, houseSize, houseSize);

Now paste the code in a file roofRow.pde and do the following.

• Run the program and check if the loop output corresponds to your prediction.
• The resulting image does not contain the rectangle drawn by the last line of code.
  Uncomment and complete the line that is used to assign a value to houseX. The goal is to make visible the rectangle for the front of the first house.
• Change the boolean value of the variable boring to execute a different branch of the if structure. Run the program many times: does the output make sense?
• Add a while loop around the last line of the program to produce an image similar to the following one.

  

• Change the code to use only one while loop since the two sequential loops can be collapsed together. Submit this code version.

2. [4 pts] Write a program palette that creates an output similar to this image.
Hint: The colors are assigned randomely. Another run of the program will produce different colors.

How can you assure that no random color is too close to the background white?

Bonus Draw many times an object made of multiple shapes: denser the pattern the better to practice nested loops. Add some variation to make it more fun.