Lua For Loops

A numeric for loop is a loop that counts from a first value to a last value. It moves the counting variable by a step value on each pass.

Count from 1 to 5

The loop starts at 1 and ends at 5. Both end values are included.

for i = 1, 5 do
  print(i)
end

Even numbers with step 2

A step of 2 jumps over every second number. The count lands on even numbers only.

for i = 2, 10, 2 do
  print(i)
end

Count down with step -1

A step of -1 counts down from 10 to 1. A final line prints after the loop ends.

for i = 10, 1, -1 do
  print(i)
end
print("Blast off")

Example

for i = 1, 5 do
  print(string.format("%d x %d = %d", 7, i, 7 * i))
end

Key points

Numeric for loop: you give a start, a limit, and an optional step.
Inclusive limits: both the first and the last value run.
Default step: with no step written, the step is 1.
Negative step: a step of -1 counts down toward the limit.
Loop variable: the counting variable belongs to the loop and stops with it.

In this example, the loop counts i from 1 to 5. Each pass formats one line with 7, the current i, and their product. The lines build the 7 times row in order.

Note

a for loop in Lua works out its start, limit, and step once, before the first pass.

Try it Yourself

Edit the code, then press Run.

Running is simulated

for i = 1, 5 do
  print(string.format("%d x %d = %d", 7, i, 7 * i))
end

Exercise

What is the last value printed by a loop that runs for i = 1, 4 and prints i?

4 3 5 1