Numeric for Loops

for i = 1, 5 do
  io.write(i, " ")
end
print()

for i = 10, 0, -5 do
  io.write(i, " ")
end
print()

for i = 0, 1, 0.25 do
  io.write(tostring(i), " ")
end
print()

1 2 3 4 5
10 5 0
0.0 0.25 0.5 0.75 1.0

• for i = start, stop, step do — both ends are inclusive.
• The step defaults to 1; a negative step counts down. A float step makes i a float (0.0, 0.25, ...).
• i is local to the loop; it doesn't exist afterwards.
• The start, stop, and step are evaluated once, before the loop starts.

Don't assign to the loop variable inside the loop: in Lua 5.4 it doesn't affect the loop, and in Lua 5.5 it's a compile error.

Nested loops

for row = 1, 3 do
  local line = ""
  for col = 1, 3 do
    line = line .. string.format("%4d", row * col)
  end
  print(line)
end

   1   2   3
   2   4   6
   3   6   9

Practice

Print the 5 times table from 5 x 1 = 5 to 5 x 10 = 50.

for n = 1, 10 do
  print(string.format("5 x %d = %d", n, 5 * n))
end

5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50