How do I convert a math operator character to perform its operation?

Question

I am trying to do something like this. It is giving me an error, which I guess is because op is a string. Is it possible to convert a string of a math operator to be an operator?

def calc(op)
  a = 9
  b = 5
  a op b
end

p calc('-')
p calc('+')

Answer 1

Here it is using Object#send:

def calc(op)
  a = 9
  b = 5
  a.send(op,b)
end

p calc('-')
p calc('+')
# >> 4
# >> 14