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Help with quiz-like chess program (Read 3502 times)

PhiLho

Re: Help with quiz-like chess program
Reply #15 - May 15^th, 2010, 1:16am

blindfish wrote on May 14^th, 2010, 11:45pm:

You also have some syntax errors: [...] A single equal sign is the assignment operator so you shouldn't be using it in conditions...

It can happens only with booleans, in Java.
That's one of the reason why I recommend to use a more logical (in both sense of word!), more readable () and terser syntax:
Code:

if (key == 'h') {
   if (!help) {
     help = true;
   }
   else if (help) {
     help = false;
   }
 }

Ie. use the booleans in tests for what they are.
Beside, this can be simplified:
Code:

if (key == 'h') {
   if (help) {
     help = false;
   }
   else {
     help = true;
   }
 }

If it is not true, it is necessarily false...
Actually, I prefer to write:
Code:

if (key == 'h') {
   help = !help;
 }

fully leveraging the boolean arithmetic...

blindfish

Re: Help with quiz-like chess program
Reply #16 - May 15^th, 2010, 3:45pm

Sorry - confused: what can only happen with booleans in Java?

Ah - I see: you mean assignment within a condition... If you try it, for example, with an int you get a compile error. Is there a good reason why the boolean doesn't throw a compile error but instead assigns the value? That's the sort of thing that produces evil bugs that can be hard to track down - especially for beginners...

Agree fully with everything in your post about using booleans; though in this context - where you want something displayed for as long as the key is pressed and then hidden on release - you do need to change the boolean state on keyReleased() rather than toggling on keyPressed(); otherwise you encounter the key repeat issue already mentioned.

The boolean assignment for toggling can be incredibly useful though Wink

Where is the what if the what is in why?

check2010

Re: Help with quiz-like chess program
Reply #17 - May 15^th, 2010, 4:25pm

Thanks guys. I'm gonna use the same boolean if-statement format that I used for my boolean variable "isPressed" (to determine if a, b, c or d is pressed).

So I have:

Code:


if (key == 'h') {
    if (help == true) {
	help = false;
    }
    else {
	help = true;
    }
    background(125, 0, 0);
    textFont(Perpetua, 30);
    text("Test", 0, 25);
  }

I keep my keyReleased() method the same:

Code:


void keyReleased() {
   response = null;
}

Yet when I press "h", the screen appears white, and stops being white when I release "h". I set the background to be red, so I don't know why it would be white (as default?).

The word "Test" is only flashed when I press/release "h". I think the problem has to do with it not being in draw(), but it shouldn't be, because it's its own function.

My other boolean variable, isPressed, works just fine:

Code:


if (key == 'a' || key == 'b' || key == 'c' || key =='d') {
    if (isPressed == true) {
	isPressed = false;
    } 
    else {
	isPressed = true;
    }
    response = tactic[tNumber].checkAnswer(key);
    background(125, 0, 0);
    fill(255);
    text(response, 0, 25);
    if (response == "Correct.") {
	tNumber = tNumber + 1;
    }
  }

Any ideas?

blindfish

Re: Help with quiz-like chess program
Reply #18 - May 16^th, 2010, 12:46am

check2010 wrote on May 15^th, 2010, 4:25pm:

The word "Test" is only flashed when I press/release "h". I think the problem has to do with it not being in draw(), but it shouldn't be, because it's its own function.

It's too early for me to explain why one works and the other doesn't, but the solution is to move the following into draw() and inside an appropriate condition:

Code:

if (help) {
  background(125, 0, 0);
  textFont(Perpetua, 30);
  text("Test", 0, 25);
}

Where is the what if the what is in why?

PhiLho

Re: Help with quiz-like chess program
Reply #19 - May 16^th, 2010, 3:37am

blindfish wrote on May 15^th, 2010, 3:45pm:

you mean assignment within a condition... If you try it, for example, with an int you get a compile error. Is there a good reason why the boolean doesn't throw a compile error but instead assigns the value

I think it goes back to the C roots/inheritance of the Java language: assignment has a value which can be used in conditions.
Except than in C, there are no booleans, 0 is seen as false, any other value is seen as true. So you can write if (a = b) print("b is true"); for example. It is more used in code like: while (c = getchar()) use(c); where you assign a value and test its value at the same time. Seductive because it is terse, but prone to errors...
In Java, you can only use booleans in conditions, there is no rule like 0 is false and 1 is true. Hence the "restriction" you wonder above.

blindfish

Re: Help with quiz-like chess program
Reply #20 - May 16^th, 2010, 2:33pm

Thanks PhiLho - that makes some sense - i.e. sounds like it's something of an anachronism... I must admit I favour writing long-hand code to aid readability rather than terse code; though of course this has its place (e.g. jquery.min which reduces the size of the download - but I sure as hell wouldn't want to work from the source code).

@check2010
I was half-asleep when I answered this morning. The reason the text in the other condition is persistent is because it's within the checkAnswer() method; which is being called every frame in draw()...

Where is the what if the what is in why?

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