A small demonstration of how to use string interpolation in a Citrus grammar.

days.rb

require 'citrus'

Citrus.eval(<<'CODE')
grammar Days
  rule every_n_days
    ('every ' number ' days') {
      "INTERVAL=#{number}"
    }
  end

  rule number
    [0-9]+
  end
end
CODE

# grammar :Days do
#   rule :every_n_days do
#     all('every ', :number, ' days') {
#       "INTERVAL=#{number}"
#     }
#   end
# 
#   rule :number do
#     /[0-9]+/
#   end
# end

if $0 == __FILE__
  require 'test/unit'

  class DaysTest < Test::Unit::TestCase
    def test_every_n_days
      match = Days.parse('every 5 days')
      assert(match)
      assert_equal('INTERVAL=5', match.value)

      match = Days.parse('every 365 days')
      assert(match)
      assert_equal('INTERVAL=365', match.value)
    end
  end
end