"cannot convert float to boolean"

Processing Beginners
1

I was trying to make a DVD screensaver and I’ve come this message “cannot convert float to boolean”
I don’t know how to fix it but this is my code to all the geneses on this platform

float x = 240;   // x location of square
float y = 0;     // y location of square

float xspeed = 5;   // speed of square on x axis
float yspeed = 5;   // speed of square on y axis


void setup() {
  size(1920, 1080);
frameRate(144);
/////
/////
/////
}

void draw() {
  background(255);

  // Display the square

  fill(175);
  stroke(0);
  rectMode(CENTER);
  rect(x, y, 100, 100);

  // movement
  
y = y + yspeed;
  x = x + xspeed;

  // bounce

  if(x = 1870){  //////// highlighted
    xspeed = xspeed * -1;
  }
  if(y = 1030){
    yspeed = yspeed * -1;
  }
}
1 Like
2

One of the things that might see kinda weird about java if you haven’t used it much, is you have to use double equals like == if you want to check if something is equals. If your goal is to check if x is equal to 1870 then try if (x == 1870) { and so on. You’ll have to do the same for the line 3 below that one too.

2 Likes
3

good find, but as

x +=5;

is used might need something like

if ( x >= 1870 )
4 Likes
4

The exact problem is that = and == are 2 completely different operations.
Say, for example, x is a float value. Then the operation x=5 sets x to 5 - and it also returns the value of x.

So, if(x = 1870){... sets x to 1870, and the operation, as a result, returns 1870 too, so you are practically doing if(1870){.... And that’s why you get an error - if statement expects a boolean value, but gets a float - and there is no direct obvious way to convert a float value to a boolean, so it just errors at you instead.

That’s why doing something like x = y = z = 12345; works - it gets resolved as x = (y = (z = 12345));, then x = (y = 12345);, then x = 12345;, practically setting every value to the deepest one in the operation chain - which is the rightmost in this case.

This can be useful to crunch up code to make it smaller or look cool. For example if(x = x+1 == 20) ... sets x to itself plus 1, and then compares that to 20, and does the if statement based on the result. (although I personally don’t like doing stuff like that)

The == operation, however, does not set anything to anything, takes 2 arguments, and returns a boolean.
So, x == 1870 gets resolved into either true or false - exactly what if(...) statement wants.

You could also combine both operations the other way around: myBool = x == 1870; - this compares x to 1870 and sets myBool to either true or false depending on the result.

As far as I know, this is also the case in many other programming languages that differentiate the two operations.

Make sure to not repeat this mistake you made when comparing boolean statements - it will give no error, would set the left boolean to the right one’s value, and can easily cause a “what in the world is going on???” moment!

3 Likes
5

Thank you but now ive got a different problem while trying to add a sprite and it says "dvd cannot be resolved to a variable

float x = random(200,300);   // x location of square
float y = random(200,300);     // y location of square
float xspeed = 1;   // speed of square
float yspeed = 1;   // speed of square


void setup() {
  size(800, 600);
frameRate(240);
//surface.setResizable(true);
PImage dvd;          /// dvd
dvd = loadImage("dvd.png"); /// dvd

}

void draw() {
  background(255);

fill(0,0,0);
rect(0,0,10000,-1);


  // Display the square
  fill(dvd); /// highighted line
  stroke(0);
  rect(x, y, -200, -150);

  // Add speed to location.
  y = y + yspeed;
  x = x + xspeed;
  // bounce
  if(x > width){
    xspeed = xspeed * -1;
  }
  if(y > height){
    yspeed = yspeed * -1;
  }
    if(x < 200){
    xspeed = xspeed * -1;
  }
  if(y < 150){
    yspeed = yspeed * -1;
  }
if (keyPressed) {
    if (key == 'b' || key == 'B') {
      xspeed = xspeed - 0.1f;
      yspeed = yspeed - 0.1f;
    }
  }
6

pls. do not answer here!

7

i fixed it…
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