Sometimes the value of our variables need to be adjusted. We know that we can update our variables using arithmetic operators like this:

var age = 99 age = age + 1 print(age) // Prints 100

We also have the option of using compound assignment operators, a shorthand method for modifying the value of variables.

If we wanted to rewrite our previous code using a compound assignment operator (+=), our syntax would look like this:

var age = 99 age += 1 print(age) // Prints 100

Notice that by using a compound assignment operator, we no longer need to reference age twice!

Here are some different compound assignment operators we can use:

  • += add and assign the sum.
  • -= subtract and assign the difference.
  • *= multiply and assign the product.
  • /= divide and assign the quotient.
  • %= divide and assign the remainder.

Check out these operators in action as we modify the value of dollars five times using compound assignment operators:

var dollars = 5 dollars += 4 // same as dollars = 5 + 4 print(dollars) // Prints: 9 dollars -= 3 // same as dollars = 9 - 3 print(dollars) // Prints: 6 dollars *= 5 // same as dollars = 6 * 5 print(dollars) // Prints: 30 dollars /= 6 // same as dollars = 30 / 6 print(dollars) // Prints: 5 dollars %= 2 // same as dollars = 5 % 2 print(dollars) // Prints: 1

While the value of dollars started out as 5, the value changed every time we used a compound assignment operator; by the end of the program, dollars had a value of 1.

When using compound assignment operators, be sure to include a space before and after the assignment operator =; otherwise, we will receive an error.



Imagine being the owner of a small fruit stand. To start the day, there are 16 apples in the inventory.

Suppose a customer comes in and buys 4 apples. Use a compound assignment operator to adjust the value of apples.


Another customer purchases half of the available apples.

Underneath your previous code, change the value of apples to reflect this exchange using a compound assignment operator.

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