a port of the Processing Visualization Language

VariableScope

Variables may either have a global or local "scope". For example, variables declared within either the setup() or loop() functions may be only used in these functions. Global variables, variables declared outside of setup() and loop(), may be used anywhere within the program. If a local variable is declared with the same name as a global variable, the program will use the local variable to make its calculations within the current scope. Variables may be localized within classes, functions, and iterative statements.

Original Processing.org Example: VariableScope

// All Examples Written by Casey Reas and Ben Fry

// unless otherwise stated.

int a = 20;  // Create a global variable "a"



void setup() 

{

  size(200, 200);

  background(51);

  stroke(255);

  noLoop();

}



void draw()

{

  // Draw a line using the global variable "a"

  line(a, 0, a, height);

  

  // Create a new variable "a" local to the for() statement 

  for(int a=50; a<80; a += 2) {

    line(a, 0, a, height);

  }

  

  // Create a new variable "a" local to the loop() method

  int a = 100;

  // Draw a line using the new local variable "a"

  line(a, 0, a, height);  

  

  // Make a call to the custom function drawAnotherLine()

  drawAnotherLine();

  

  // Make a call to the custom function setYetAnotherLine()

  drawYetAnotherLine();

}



void drawAnotherLine() 

{

  // Create a new variable "a" local to this method

  int a = 185;

  // Draw a line using the local variable "a"

  line(a, 0, a, height);

}



void drawYetAnotherLine() 

{

  // Because no new local variable "a" is set, 

  // this lines draws using the original global

  // variable "a" which is set to the value 20.

  line(a+2, 0, a+2, height);

}
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