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Syntax of functions

There are two parts of a function. First there is the the function declaration, where the name of the function along with its properties and behaviors are defined. Next there is the function call, where the function is then actually executed. Functions may be called multiple times.

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Functions can also return a value. This means when we return to the line where the function was called, it has now carried a number with it. In processing, functions that have no return value are declared with “void” return type.

Function Declaration

This is how the function is named, its return type and parameters defined with sudo code.

datatype functionName datatype functionName (parameter,.....)

{

<function contents>

<possible return value>

}

Function call 

This is how we execute a function:

functionName(parameter,.....) ;

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Function Examples

This example shows how to write functions with return values.

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This example shows how to use functions around the code of for creating legible and simple blocks (modularization).

void setup()
{
  size(300500,300);
  smoothstroke(255);
  stroke(255,255,255strokeWeight(3);
  noFill();
}
 
void draw()
{
  background(0);
    bommelsmiley(100,10,140,50height/2);
  bommelsmiley(150,10,190,50250,height/2);
  bommelsmiley(200,10,240,50400,height/2);
}
 

void bommelsmiley(int x, int y,int length,int size)
{
  strokeWeightprintln(1"smiley");
  lineellipse(x,y,100,100);  // head
  
  ellipse(x - 20,y+length); - 10,10,15);  // left eye
  strokeWeight(5);ellipse(x + 20,y - 10,10,15);  // right eye
   
  ellipsearc(x,y+length,size,size);,60,60,radians(20),radians(180-20));  // mouth
}

And here is our first interactive program:

void setup()
{
  size(300,300);
  background(0);
}
 
void draw()
{}
 
void mousePressed()
{
  println("x:" + mouseX + ", y:" + mouseY);
}

Exercise 4

Create Write a Programm sketch where a unique shape follows the mouse position. When you click the mouse, the shape should change in some way (form, colour, size).