Processing: Control Logical Operators

Front 1

! (logical NOT)

Back 1

Inverts the Boolean value of an expression. Returns true if the expression is false and returns false if the expression is true. If the expression (a>b) evaluates to true, then !(a>b) evaluates to false.

Example
boolean a = false;
if (!a) {
rect(30, 20, 50, 50);
}
a = true;
if (a) {
line(20, 10, 90, 80);
line(20, 80, 90, 10);
}

Syntax
!expression

Front 2

&& (logical AND)

Back 2

Compares two expressions and returns true only if both evaluate to true. Returns false if one or both evaluate to false. The following list shows all possible combinations:

true && false // Evaluates false because the second is false
false && true // Evaluates false because the first is false
true && true // Evaluates true because both are true
false && false // Evaluates false because both are false

Example
for (int i = 5; i <= 95; i += 5) {
if ((i > 35) && (i < 60)) {
stroke(0); // Set color to black
} else {
stroke(255); // Set color to white
}
line(30, i, 80, i);
}

Syntax
expression1 && expression2

Front 3

|| (logical OR)

Back 3

Compares two expressions and returns true if one or both evaluate to true. Returns false only if both expressions are false. The following list shows all possible combinations:

true || false // Evaluates true because the first is true
false || true // Evaluates true because the second is true
true || true // Evaluates true because both are true
false || false // Evaluates false because both are false

Example
for (int i = 5 ; i <= 95; i += 5) {
if ((i < 35) || (i > 60)) {
line(30, i, 80, i);
}
}

Syntax
expression1 || expression2