"If Then Else" conditional expression

Another common feature of computer programs is making decisions. Suppose, user enters two numbers and program needs to pick largest of them. General construct "if-then-else" is given by example:

a, b = io.read('*n', '*n')
if a > b then
  print(a)
else
  print(b)
end

You may note it is somewhat similar to while loop: there is a condition (a > b in our case) - then some code which executes if the condition is true. Just it doesn't repeat. And additionally there is different code to be executed if condition is wrong. These parts are divided by keywords:

if {condition} then {code-for-true} else {code-for-false} end

Additionally you may have noticed we used io.read with two arguments to read two variables in a single statement, one after another. We'll discuss this in more details later, for now just remember this as useful trick.

For exercise, try modifying this program so that:

• it enters single number, person's height in feet
• if it is less than 5.5 it prints short
• if it is more than 6.5 it prints tall
• otherwise it prints average

Obviously this couldn't be done with single if-else statement, so you can "nest" one conditional structure inside any "branch" of another one:

if {something} then
  if {another_check} then ...
  else ... end
else ... end

Among our general problems there is similar exercise too: Minimum of Two!