Module 09 : User-defined Functions

• Topics
• Resources
• In-Class Activities
• Sample Quiz Question

Topics

• User-defined functions

New processing syntax:

• Basics of a function signature:

      returnType functionName(parameters) {
          functionBody
      }
      

Resources

• My own notes

• Watch Daniel Shiffman Video 7.1, Function Basics (9 minutes)
  (available at learningprocessing.com and YouTube)

• Watch Daniel Shiffman Video 7.2, Modularity with Functions (9 minutes)
  (available at learningprocessing.com and YouTube)

• Watch Daniel Shiffman Video 7.3, Reusability with Functions (7 minutes)
  (available at learningprocessing.com and YouTube)

• Watch Daniel Shiffman Video 6.3, Variable Scope (9 minutes)
  (available at learningprocessing.com and YouTube)

• Ch. 9 of the Reas/Fry book (pp. 121-133) is good for motivation (but they are using some techniques that we haven't yet seen from Chapter 6 of that book.

In-Class Activities

Try to recreate any of the following interactive sketches on your own.

Flags
Implement a function that has signature as follows.

void flag(int x, int y, int w, int h, color a, color b, color c)

void setup() {
  size(450, 100);
  flag(25,25,80,60,color(0), color(227,0,19), color(255,205,70));     // Germany
  flag(125,25,80,60,color(255), color(7,32,245), color(255,0,23));    // Russia
  flag(225,25,90,60,color(178,25,43), color(255), color(31,72,135));  // Netherlands
  flag(325,25,90,60,color(243,36,61), color(255), color(243,36,61));  // Austria
}

Implementation: spoiler

Ladder
Implement a function that has signature as follows.

void ladder(int x, int y, int w, int h, int n)

void setup() {
  size(300, 400);
  ladder(50, 50, 20, 200, 10);
  ladder(100, 50, 40, 300, 30);
  ladder(175, 200, 80, 80, 3);
}

Implementation: spoiler

Caterpillar
Implement a function that has signature as follows.

void caterpillar(int x, int y, int r, int n)

void setup() {
  size(500, 200);
  fill(0, 200, 0);
  caterpillar(50, 50, 20, 10);
  caterpillar(50, 100, 10, 5);
  fill(255, 255, 0);
  caterpillar(100, 150, 10, 10);
}

Implementation: spoiler

Random Colors
We have seen several examples where we wanted to use a randomly chosen color for some purpose. The syntax for doing so is a bit bulky, and if you wanted to use random colors in several different places within your code, it might be worthwhile to implement a function that could be called with syntax randomColor() and which would return the random color. Implement such a function and then demonstrate its use to complete the following sketch:

void setup() {
  size(500,400);
  strokeWeight(5);
}

void draw() {
  fill(randomColor());
  stroke(randomColor());
  ellipse(random(width), random(height), 30, 30);
}

// your part here...

Implementation: spoiler

Growing Smiley
A varient of last module's growing circle. This time we use a funciton that draws a smiley face with a given center and scale. To get you going, we provide our code that implements a drawFace function and a drawFaceMessage function. See if you can use those to achieve the growing effect.

Implementation: spoiler

Sunrise, Sunset
For our next example, we begin by providing a static sketch of a scene with a house (house.pde). Your goal is to redesign the code so that it toggles between daytime and nighttime with each mouse click. We would like you to use separate functions for the two versions, but ideally to have yet another function that encapsulates all of the commands that are common to both versions.

Implementation: spoiler

Sample Quiz Question