Conditional statements: if

Very often, you need to make choices in your program: Some actions need to happen only when particular situations occur. For that, you can use conditions that allow you to control the flow of your program.

 

real life: if you are hungry, get something to eat //it is not really healthy to eat all the time...

growing circle: if the circle exceeds the screen, it should start over.

 

A conditional statement has always 2 parts:

chart-if

* Conditions are expressions (combinations of values and operators) that evaluate to true (yes) or false (no) (true and false are reserved words)

* If the condition is true (and only then), the code inside the {} will be executed. Afterwards, the program continues with the next statement after the {}

*If the condition is false, the code inside the {} is SKIPPED and the program jumps to the first statement after the {}

How do you write conditions? Relational operators

Less than <
Greater than >
Equal ==
Not equal !=
Less or equal <=
Greater or equal >=

Expression In plain English... Answer
2>3 is 2 greater than 3? no, false
5>3 is 5 greater than 3 ? yes, true
2==3 is 2 equal to 3? no, false
pow(2,3)>0 is the result of pow(2,3) greater than 0? yes, true
x>=0 is x greater or equal to 0? it depends!

 

*IMPORTANT! Do not confuse '=' (assignment) with '=='(equality)

x=1; //give variable x the value 1

x==1 // is x equal to 1?

Examples

if (my_var>5) { //is my_var greater that 5? if yes
rect(100,100,20,20); // draw a rectangle
}
//what will this draw for my_var=1, my_var=10, my_var=5?

--------------------------------------------------

if (my_var>5) {
rect(100,100,20,20);
}
ellipse(50,50,20,20);

//what will this draw for my_var=1, my_var=10, my_var=5?

So, how can I make my growing circle smarter?

In words: if the circle exceeds the screen, it should start over.

 

if (exceeds the screen) { //but what does "exceed the screen" actually mean?

start over //and how does it start over?

}

--------------------------------------------------

//a smarter growing circle
int diameter=0;
void setup() {
size(200,200);
}
void draw() {
diameter=diameter +1;
if (diameter>width) {
diameter=0;
}
ellipse(width/2,height/2,diameter,diameter);
}