Logical Operators
Logical AND Operator

The logical, &&, operator evaluates two operands and returns a Boolean result. It returns true only when both operands are true and returns false when at least one operand is false.

&& is denoted by two ampersand symbols and translates to AND.

The following truth table demonstrates all of the possible outcomes of an expression using &&.

Logical Expression Result
true && true true
true && false false
false && true false
false && false false

Let’s see the && operator in action. Assume we’re writing a program for an application that dims a screen by 25% in the evening time. We can set up the following if/else statement for this case:

var time = 8 // PM var phoneInUse = true var brightness: Double if time >= 8 && phoneInUse { brightness = 0.75 } else { brightness = 1 } print(brightness) // Prints: 0.75

Notice how the brightness will be set to 75% only when time >= 8 and phoneInUse are both true. Changing the value of time to be less than 8 or setting phoneInUse to false, would result in the brightness remaining the same.



In NewYear.swift, we’ve declared the variables, midnight and date to be used within our New Year program.

Below the variables, create an if statement that:

  • Checks if it is midnight AND the date is "January 1, 2020".
  • Prints the message, "It's the start of a new decade!".

Continue practicing in the editor by testing your code with different values for midnight or date. Make sure your code is working as expected before moving on.

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