Numbers

print can print numbers too. Numbers are written without quotes, and Lua can calculate with them. When you put a calculation in the parentheses, Lua works it out first and prints the result:

print(42)
print(7 + 5)
print(20 - 9)
print(3 * 4)
print(5 - 8)

This prints:

42
12
11
12
-3

For the basic arithmetic, Lua uses these operators (symbols for operations):

• + addition
• - subtraction
• * multiplication (a star, because there is no × on the keyboard)
• / division

A calculation in quotes is a text, and a text is printed exactly as it is written: print("7 + 5") prints 7 + 5.

As in math, multiplication and division come before addition and subtraction, and operations of the same level are done from left to right. If you want a different order, use parentheses:

print(2 + 3 * 4)
print((2 + 3) * 4)

This prints:

14
20

In the first line, Lua multiplies 3 * 4 first, which is 12, and then adds 2. In the second line, the parentheses make it add 2 + 3 first, and only then multiply the 5 by 4.

Division has one surprise:

print(7 / 2)
print(10 / 2)

This prints:

3.5
5.0

Division with / always gives a decimal number, even when the result is whole, so 10 / 2 prints 5.0, not 5. It's the same value, just a different kind of number. Lua has two kinds of numbers, whole and decimal, and you'll learn all about them in the next lesson.

Decimal numbers are written with a dot, 2.5, never with a comma (you'll see why in the next exercise). Write big numbers without spaces or commas, too: 1250, not 1 250 or 1,250. The spaces around operators, on the other hand, don't change anything; they just make the code easier to read. And multiply with *, not with the letter x: print(3 x 4) ends with an error.