puppetlabs-stdlib/lib/puppet/parser/functions/range.rb

#
# range.rb
#

# TODO(Krzysztof Wilczynski): We probably need to approach numeric values differently ...

module Puppet::Parser::Functions
  newfunction(:range, :type => :rvalue, :doc => <<-EOS
When given range in the form of (start, stop) it will extrapolate a range as
an array.

*Examples:*

    range("0", "9")

Will return: [0,1,2,3,4,5,6,7,8,9]

    range("00", "09")

Will return: [0,1,2,3,4,5,6,7,8,9] (Zero padded strings are converted to
integers automatically)

    range("a", "c")

Will return: ["a","b","c"]

    range("host01", "host10")

Will return: ["host01", "host02", ..., "host09", "host10"]

Passing a third argument will cause the generated range to step by that
interval, e.g.

    range("0", "9", "2")

Will return: [0,2,4,6,8]
    EOS
  ) do |arguments|

    raise(Puppet::ParseError, 'range(): Wrong number of ' +
      'arguments given (0 for 1)') if arguments.size == 0

    if arguments.size > 1
      start = arguments[0]
      stop  = arguments[1]
      step  = arguments[2].nil? ? 1 : arguments[2].to_i.abs

      type = '..' # Use the simplest type of Range available in Ruby

    else # arguments.size == 1
      value = arguments[0]

      if m = value.match(/^(\w+)(\.\.\.?|\-)(\w+)$/)
        start = m[1]
        stop  = m[3]

        type = m[2]
        step = 1
      elsif value.match(/^.+$/)
        raise(Puppet::ParseError, "range(): Unable to compute range " +
          "from the value: #{value}")
      else
        raise(Puppet::ParseError, "range(): Unknown range format: #{value}")
      end
    end

    # If we were given an integer, ensure we work with one
    if start.to_s.match(/^\d+$/)
      start = start.to_i
      stop  = stop.to_i
    else
      start = start.to_s
      stop  = stop.to_s
    end

    range = case type
      when /^(\.\.|\-)$/ then (start .. stop)
      when '...'         then (start ... stop) # Exclusive of last element
    end

    result = range.step(step).to_a

    return result
  end
end

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