User Tools

Site Tools


courses:2009.10.13.intro_prototyping

oct 13: Introduction to programming with Processing: variables and functions

Variables

In summary: a variable is a container with a name and content (memory space). It is used to store a value.

In Processing you have specifically declare the type of variables you are using:

boolean a = true   // create a variable "a" of the type "boolean" (true or false)
int b = 0;         // create a variable "b" of the type "int" (integer)
float c = 0.0;     // create a variable "c" of the type "float" (number with decimal precision)
byte d = 127       // create a variable "d" of the type "byte" (number between 127 and -128) 
char e = 'A'       // create a variable "e" of the type "char" (character)

File built during the class: variables_00.zip

// declare our variables, at the right level/scope so they are accessible throughout the program
int circleSize = 15;
int circleX = 20;
int startX = 100;
int startY = 20;
int delta = 40;

void setup(){

  size(600,400);
  smooth();
  frameRate(30);
  println("starting up");

}


void draw(){

  // println("loop");
  // background(100);
  fill(100, 10);
  rect(0, 0, width, height);


  // startX  = mouseX;
  // startY = mouseY
  delta = mouseX;


  // 10x10 circles
  for(int counterY = 0; counterY <10 ; counterY = counterY + 1){

    for(int counter = 0; counter < 10 ; counter = counter + 1){ 
      // println("counter: " + counter);
      fill(255);
      ellipse(startX + delta * counter, startY + delta * counterY, circleSize, circleSize);
    }

  }

}

Functions

  • a structured block of code
  • it has a type, a name and can have parameters (values passed to it)

A simple function of type void called setup and it requires no parameters

void setup(){

}

Another function called fill and it can have different number of parameters

fill(0);             // greyscale
fill(100, 200);      // greyscale and alpha
fill(255, 0, 0);     // RGB
fill(255, 0, 0, 20); // RGB and alpha
courses/2009.10.13.intro_prototyping.txt · Last modified: 2010/11/03 00:45 by 130.239.61.133