Lua Academy · Lesson

Arithmetic and Relational Operators

Use +, -, *, /, //, %, ^ and comparison operators effectively.

Arithmetic Operators Overview

Lua provides a full set of arithmetic operators: + (add), - (subtract), * (multiply), / (float divide), // (floor divide), % (modulo), ^ (exponentiation), and unary - (negation). Understanding when each returns an integer vs float is crucial in Lua 5.3+.

print(10 + 3)   -- 13
print(10 - 3)   -- 7
print(10 * 3)   -- 30
print(10 / 3)   -- 3.3333...  (always float)
print(10 // 3)  -- 3          (floor division)
print(10 % 3)   -- 1          (modulo)
print(2 ^ 10)   -- 1024.0     (always float)
print(-5)       -- -5

Integer vs Float Division

The / operator always returns a float, even when dividing two integers that divide evenly. The // floor division operator returns an integer only when both operands are integers; if either is a float, the result is a float but still rounded down.

The ^ exponentiation operator always converts to float, so 2^3 gives 8.0, not 8. Use math.tointeger() to convert back if needed.

print(6 / 2)        -- 3.0  (float!)
print(6 // 2)       -- 3    (integer)
print(6.0 // 2)     -- 3.0  (float floor)
print(7 // 2)       -- 3    (floor toward -inf)
print(-7 // 2)      -- -4   (floor, not truncate!)
print(2 ^ 3)        -- 8.0  (always float)

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