Comments on: Exercise 7-6: Parameter Passing

By: Daniel Shiffman

Daniel Shiffman — Sun, 21 Mar 2010 23:27:56 +0000

If the variable is not global, it is simply reset each time back to 50 and therefore never has the chance to increment.

By: Patrick mimran

Patrick mimran — Sat, 20 Mar 2010 11:54:52 +0000

Hello

there is something i do not understand ,
i made my function called monDessin and i try to animate monDessin it only works when my variable is global , if i put movex inside myDessin no mouvement , why ?

Thanks you for your time

Patrick

like in this code :
float movex = 50 ;
void setup () {
size ( 300 , 300 ) ;
}
void draw () {
background ( 100 ) ;
monDessin () ;
}
void monDessin () {
fill ( random (0 , 255) , 100 , 200 ) ;
movex = movex + 1 ;
rect ( movex , 20 , 50 , 50 ) ;
ellipse ( movex , 80 , 50 , 10 ) ;
}

but if i move , movex inside myDessin function as below it does not work , Why ?

void setup () {
size ( 300 , 300 ) ;
}
void draw () {
background ( 100 ) ;
monDessin () ;
}
void monDessin () {

float movex = 50 ;
fill ( random (0 , 255) , 100 , 200 ) ;
movex = movex + 1 ;
rect ( movex , 20 , 50 , 50 ) ;
ellipse ( movex , 80 , 50 , 10 ) ;
}

By: Patrick Mimran

Patrick Mimran — Fri, 12 Mar 2010 23:13:06 +0000

thank you

Patrick Mimran

By: Daniel Shiffman

Daniel Shiffman — Fri, 12 Mar 2010 16:56:04 +0000

I think what you want to do is:

void setup() {
  int val1 = multos(2,3);
  int val2 = multos(4,5);
  println(val1);
  println(val2);
}

int multos(int a, int b) {
  return a*b;
}

By: Patrick Mimran

Patrick Mimran — Fri, 12 Mar 2010 15:40:55 +0000

in the exercise 7-5

this is what i have done , but i am sure there is a simpler way to condense int total = a * b ;
int total2 = c * d ; in one line but i don not know how ?
Could you tell to me how

Thanks

P Mimran

void multos ( int a , int b , int c , int d ) {
int total = a * b ;
int total2 = c * d ;
println ( total) ;
println (total2 ) ;

}

{
multos ( 2 , 3 , 4 , 5 )

}

By: Alex

Alex — Fri, 12 Mar 2010 12:32:25 +0000

Of course, it totally makes sense
Thanks for your quick reply!

By: Daniel Shiffman

Daniel Shiffman — Thu, 11 Mar 2010 17:08:44 +0000

This is because there is only one variable 'x' for all of the balls. So x = x+speed gets called multiple times each cycle through draw(). Option one would be to have x1,x2,x3,etc. for all the balls, but a better option would be to use object-oriented programming and arrays (chapters 8 and 9). Or if all the balls really just stay together always, you could say:

void setup() {
  size(200,200);
  background(0);
  noStroke();
  fill(255);
  smooth();
  frameRate(30);
}

float x = 10;
float speed = 1;
float diam = 10;

void draw() {
  background(0);
  drawBall(30);
  drawBall(50);
  drawBall(70);
  drawBall(90);
  drawBall(110);
  drawBall(130);
  
  moveBall();
}

void drawBall(int yPos) {
  ellipse(x,yPos,diam,diam);
}

void moveBall(){
  if ((x > width-(diam/2))) {
    speed = speed*(-1);
  }
  x = x+speed;
}

By: Alex

Alex — Wed, 10 Mar 2010 22:21:13 +0000

Hi,

I wrote the following code as an exercise, and 2 things seem weird to me:
- how come all the instances of the ball are not aligned vertically?
- why do the balls move slower if I remove some of them?

Thanks in advance for your help

void setup() {
  size(200,200);
  background(0);
  noStroke();
  fill(255);
  smooth();
  frameRate(30);
}

float x = 10;
float speed = 1;
float diam = 10;

void draw() {
  background(0);
  moveBall(30);
  moveBall(50);
  moveBall(70);
  moveBall(90);
  moveBall(110); //these balls are not aligned vertically.
  moveBall(130); //the more I add, the faster they move!
}

void moveBall(int yPos) {
  if ((x > width-(diam/2))) {
    speed = speed*(-1);
  }
  x = x+speed;
  ellipse(x,yPos,diam,diam);
}