Operator Precedence

Part of the Fundamentals section of Coddy's Lua journey — lesson 16 of 90.

When you write mathematical expressions with multiple operators, Lua follows specific rules to determine which operations to perform first. This concept is called operator precedence, and it works just like the order of operations you learned in mathematics.

In Lua, multiplication and division are performed before addition and subtraction:

result = 2 + 3 * 4    -- result is 14, not 20
-- Lua calculates 3 * 4 first (12), then adds 2

result = 10 - 6 / 2   -- result is 7, not 2
-- Lua calculates 6 / 2 first (3), then subtracts from 10

To control the order of operations, you can use parentheses (). Operations inside parentheses are always performed first:

result = (2 + 3) * 4  -- result is 20
-- Lua calculates 2 + 3 first (5), then multiplies by 4

result = (10 - 6) / 2 -- result is 2
-- Lua calculates 10 - 6 first (4), then divides by 2

Challenge

Easy

Calculate the average of three test scores using proper operator precedence. Create three variables for the test scores, then write a single expression that correctly calculates their average.

Create the following variables:

score1 with the value 85
score2 with the value 92
score3 with the value 78

Write a single expression to calculate the average by adding all three scores and dividing by 3. Use parentheses to ensure the addition happens before the division. Store the result in a variable called average and print it.

Cheat sheet

Lua follows operator precedence rules where multiplication and division are performed before addition and subtraction:

result = 2 + 3 * 4    -- result is 14, not 20
result = 10 - 6 / 2   -- result is 7, not 2

Use parentheses () to control the order of operations:

result = (2 + 3) * 4  -- result is 20
result = (10 - 6) / 2 -- result is 2

Try it yourself

-- Create the test score variables
local score1 = 85
local score2 = 92
local score3 = 78

-- TODO: Write your code here to calculate the average using proper operator precedence

-- Print the result
print(average)