Module: Enumerable

Included in:
Xqsr3::Containers::FrequencyMap, Xqsr3::Containers::MultiMap
Defined in:
lib/xqsr3/doc_.rb,
lib/xqsr3/extensions/enumerable/unique.rb,
lib/xqsr3/extensions/enumerable/detect_map.rb,
lib/xqsr3/extensions/enumerable/collect_with_index.rb

Overview

Standard module, extended with methods:

  • Enumerable#collect_with_index

  • Enumerable#detect_map

  • Enumerable#unique

Instance Method Summary collapse

Instance Method Details

#collect_with_index(base = 0) ⇒ Object

Two-parameter variant of Enumerable#collect, where the second parameter is a base-based index, which increments by 1 for each enumerated element.



59
60
61
62
63
64
65
66
67
68
69
 
# File 'lib/xqsr3/extensions/enumerable/collect_with_index.rb', line 59

def collect_with_index(base = 0)

  a = []

  self.each_with_index do |element, index|

    a.push yield(element, base + index)
  end

  a
end

#detect_map(&block) ⇒ Object

The Enumerable#detect method provides a way to detect the presence of a particular value in a collection. The only constraint is that you get back the object unchanged.

The Enumerable#map method provides a way to transform the contents of a collection. The only constraint is that you get back another collection.

This extension method, Enumerable#detect_map combines the features of both, in that it detects the presence of a particular value in a collection and transform the detected value.

[ 1, 2, 3 ].detect_map { |v| -2 * v if v > 2 } # => -6

{ :ab => 'cd', :ef => 'gh' }.detect_map { |k, v| v.upcase if k == :ef } # => 'GH'

Note: The block is required (for technical reasons), and must have arity 1 for sequences or 2 for associations



71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
 
# File 'lib/xqsr3/extensions/enumerable/detect_map.rb', line 71

def detect_map &block

  case block.arity
  when 1

    self.each do |v|

      r = yield(v) and return r
    end
  when 2

    self.each do |k, v|

      r = yield(k, v) and return r
    end
  else

    raise ArgumentError, "detect_map requires block with arity of 1 (for sequences) or 2 (for associations); block with arity #{block.arity} given to instance of #{self.class}"
  end

  nil
end

#unique(&block) ⇒ Object

Removes all duplicate elements in a sequence subject to an optional two-parameter block in order to return an array containing unique elements

[ 1, 2, 3 ].unique # => [ 1, 2, 3 ]
[ 1, 2, 1, 3 ].unique # => [ 1, 2, 3 ]



62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
 
# File 'lib/xqsr3/extensions/enumerable/unique.rb', line 62

def unique(&block)

  if not block

    return unique { |a, b| a == b }
  else

    raise ArgumentError, "block requires two parameters" unless block.arity == 2

    ar = self.to_a

    return ar if ar.length < 2

    r = []
    h = {}

    ar.each do |v|

      unless h.has_key?(v)

        r << v
        h[v] = nil
      end
    end

    return r
  end
end