Define custom Ruby operator

Question

The question is: Can I define my own custom operator in Ruby, except for the ones found in \"Operator Expressions\"?

For example: 1 %! 2

Answer 1

No. You can only define operators already specified in ruby, +,-,!,/,%, etc. (you saw the list)

You can see for yourself this won't work

def HI
  def %!
    puts "wow"
  end
end

This is largely due to the fact that the syntax parser would have to be extended to accept any code using your new operator.

---

As Darshan mentions this example alone may not be enough to realize the underlying problem. Instead let us take a closer look at how the parser could possibly handle some example code using this operator.

3 %! 0

While with my spacing it may seem obvious that this should be 3.%!(0) without spacing it becomes harder to see.

3%! can also be seen as 3.%(0.!) The parser has no idea which to chose. Currently, there is no way easy way to tell it. Instead, we could possibly hope to override the meaning of 3.%(0.!) but this isn't exactly defining a new operator, as we are still only limited to ruby's parsable symbols

Answer 2

Yes, custom operators can be created, although there are some caveats. Ruby itself doesn't directly support it, but the superators gem does a clever trick where it chains operators together. This allows you to create your own operators, with a few limitations:

$ gem install superators19

Then:

require 'superators19'

class Array
  superator "%~" do |operand|
    "#{self} percent-tilde #{operand}"
  end
end

puts [1] %~ [2]
# Outputs: [1] percent-tilde [2]

Due to the aforementioned limitations, I couldn't do your 1 %! 2 example. The Documentation has full details, but Fixnums can't be given a superator, and ! can't be in a superator.

Answer 3

You probably can't do this within Ruby, but only by modifying Ruby itself. I think modifying parse.y would be your best bet. parse.y famtour