Optional argument after splat argument

Question

Here is my program:

def calculate(*numbers, options = {})
  add(numbers)      if options[:add]
  subtract(numbers) if options[:add] == false
end

def add(*numbers)
  numbers.reduce(:+)
end

def subtract(*numbers)
  numbers.reduce(:-)
end

p calculate(1,2)

On line 1, it is complaining

tests.rb:1: syntax error, unexpected '=', expecting ')'
def calculate(*numbers, options = {})
________________________________________________^
[Finished in 0.1s with exit code 1]

I thought it might have been a problem with default values in Ruby, because before v1.9, you were required to have all default values in order - but this shouldn't be the issue because my version is

ruby 2.0.0p195 (2013-05-14) [i386-mingw32]

I've tried transposing the spaces all over, because ruby seems to be particular with those things when it comes to methods, but no dice.

Could it be my splat variable *numbers ?

Answer 1

You cannot have optional parameters after a splat.

The splat means "use up all of the remaining arguments" but then you provide an optional argument, so how could the interpreter know if the last argument is part of the "numbers" splat or the optional "options"?