The Book of Ruby

Testing a Condition: if..then

The problem with the simple tax calculator code shown earlier is that it accepts negative subtotals and calculates negative tax on them—a situation upon which the government is unlikely to look favorably! I therefore need to check for negative numbers and, when found, set them to zero. This is my new version of the code:

5taxcalculator.rb

taxrate = 0.175
print "Enter price (ex tax): "
s = gets
subtotal = s.to_f

if (subtotal < 0.0)  then
  subtotal = 0.0
end

tax = subtotal * taxrate
puts "Tax on $#{subtotal} is $#{tax}, so grand total is $#{subtotal+tax}"

The Ruby if test is similar to an if test in other programming languages. Note, however, that the parentheses are once again optional, as is the keyword then. However, ...