Puppet Function: values_at

Defined in:
puppet/modules/stdlib/lib/puppet/parser/functions/values_at.rb
Function type:
Ruby 3.x API

Overview

values_at() ⇒ Any

Finds value inside an array based on location.

The first argument is the array you want to analyze, and the second element can be a combination of:

  • A single numeric index

  • A range in the form of 'start-stop' (eg. 4-9)

  • An array combining the above

Examples:

values_at(['a','b','c'], 2)

Would return ['c'].

values_at(['a','b','c'], ["0-1"])

Would return ['a','b'].

values_at(['a','b','c','d','e'], [0, "2-3"])

Would return ['a','c','d'].

Returns:

  • (Any) 


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# File 'puppet/modules/stdlib/lib/puppet/parser/functions/values_at.rb', line 6

newfunction(:values_at, :type => :rvalue, :doc => <<-EOS
Finds value inside an array based on location.

The first argument is the array you want to analyze, and the second element can
be a combination of:

* A single numeric index
* A range in the form of 'start-stop' (eg. 4-9)
* An array combining the above

*Examples*:

  values_at(['a','b','c'], 2)

Would return ['c'].

  values_at(['a','b','c'], ["0-1"])

Would return ['a','b'].

  values_at(['a','b','c','d','e'], [0, "2-3"])

Would return ['a','c','d'].
  EOS
) do |arguments|

  raise(Puppet::ParseError, "values_at(): Wrong number of " +
    "arguments given (#{arguments.size} for 2)") if arguments.size < 2

  array = arguments.shift

  unless array.is_a?(Array)
    raise(Puppet::ParseError, 'values_at(): Requires array to work with')
  end

  indices = [arguments.shift].flatten() # Get them all ... Pokemon ...

  if not indices or indices.empty?
    raise(Puppet::ParseError, 'values_at(): You must provide ' +
      'at least one positive index to collect')
  end

  result       = []
  indices_list = []

  indices.each do |i|
    i = i.to_s
    if m = i.match(/^(\d+)(\.\.\.?|\-)(\d+)$/)
      start = m[1].to_i
      stop  = m[3].to_i

      type = m[2]

      if start > stop
        raise(Puppet::ParseError, 'values_at(): Stop index in ' +
          'given indices range is smaller than the start index')
      elsif stop > array.size - 1 # First element is at index 0 is it not?
        raise(Puppet::ParseError, 'values_at(): Stop index in ' +
          'given indices range exceeds array size')
      end

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

      range.each { |i| indices_list << i.to_i }
    else
      # Only positive numbers allowed in this case ...
      if not i.match(/^\d+$/)
        raise(Puppet::ParseError, 'values_at(): Unknown format ' +
          'of given index')
      end

      # In Puppet numbers are often string-encoded ...
      i = i.to_i

      if i > array.size - 1 # Same story.  First element is at index 0 ...
        raise(Puppet::ParseError, 'values_at(): Given index ' +
          'exceeds array size')
      end

      indices_list << i
    end
  end

  # We remove nil values as they make no sense in Puppet DSL ...
  result = indices_list.collect { |i| array[i] }.compact

  return result
end