Trying to limit println()

Processing Beginners
1

I am trying to run println(); once in an if statement, the if statement can be true for many frames, but the print(); should only run once.
Many thanks,
Adi

2

Good morning ADI, I think the best way to understand your issue is to post the code.

1 Like
3

I was just about to post an example, the real code is long and only a part of it has a problem. The problem is that the println(); is running many times, because it is true many times, but I can’t stop the draw from looping or slow it down. I only want the println(); to run once until it is not true, not each time it is true. Also it is 12:30 am, rightnow I will probably, be able to reply later.
Thanks,
Adi

float i = 1;
void setup() {
}
void draw() {
  mm();
}
void mm () {
  if (mousePressed == true) {
    println(i);//I want this done once, until it is not true, not each time this is true.
  } else println();
  i = i + 1;//Same over here.
}
2 Likes
4

You might try this

boolean  allowPrint = true;

void setup() {
}
void draw() {
  mm();
}
void mm () {
  if (mousePressed == true && allowPrint == true) {
    println(frameCount + " @ " + millis());
    allowPrint = false;  // this stops repetition
  } 
  if (mousePressed == false) {
    allowPrint = true; // This allows the println the next time the mouse is pressed
  }
}
4 Likes
5

One more request, what if I want the same thing happening in an if statement like this,

float a = random(0,100);
float b = random(0,100);
boolean allowprint = true;
void setup(){}
void draw(){
 rect(a,b,10,10);
    mm();
}
 void mousePressed() {
  rectX = mouseX;
  rectY = mouseY;
}
void mm (){
if (x1==a && y1==b) {
 if (x1==a && y1==b) {
     allowPrint = true;
}
    if (allowPrint==true) {
      println("hi");
      allowPrint=false;
}
if (x1==a&& y1==b== false) {
    allowPrint = false; 
  }
 }
}

(the if statements can be true for many frames), is there a way to keep, allowprint, false, and make it true only when the person wants it to be true. Also, this code might need some other corrections.

1 Like
6

Since the code won’t run then there are obvious errors which need fixing. In this case several variable have not been declared so you need to fix that.
So a quick primer on boolean expressions, boolean variables and conditional statements

A boolean expression is anything that evaluates to true or false and are used in conditional statements (e.g. if, while). A boolean variable is also a boolean expression that does not need evaluating because it is already true or false so the statement

if(allowPrint == true){... can be written if(allowPrint){...

and for false we can use the ‘not’ operator (!). !allowPrint means not allowPrint so if allowPront is true then !allowPrint is false so the statement

if(allowPrint == false){... can be written if(!allowPrint){...

Now we come to the statement in your code y1==b== false at first glance I thought this was a mistake but the syntax is permitted even if the meaning is unclear. Anyway I did work it out and

y1==b== false evaluates to true if y1 is not equal to b so can be written y1 != b

Now we come to the first two statements inside the method mm

  if (x1==a && y1==b) {    
    if (x1==a && y1==b) {

Now think about it, the second statement will only be executed if the boolean expression in the first statement is true. What this means is

  if (x1==a && y1==b) {    
    // We only get here if (x1==a && y1==b) is true
    if (x1==a && y1==b) {  // which means this will also be true so redundant

So taking these into account the function can be rewritten as

void mm () {
  if (x1 == a && y1 == b) {
    allowPrint = true;
    if (allowPrint) {
      println("hi");
      allowPrint=false;
    }
    if (x1 == a && y1 != b) {
      allowPrint = false;
    }
  }
}

If you need further help then please modify your code so it run and give a clearer explanation of what you are trying to achieve.

6 Likes