Module Enumerable
In: lib/facets/core/facets/enumerable/find_yield.rb
lib/facets/core/facets/enumerable/frequency.rb
lib/facets/core/facets/enumerable/sum.rb
lib/facets/core/facets/enumerable/each_by.rb
lib/facets/core/facets/enumerable/defer.rb
lib/facets/core/facets/enumerable/expand.rb
lib/facets/core/facets/enumerable/ewise.rb
lib/facets/core/facets/enumerable/visit.rb
lib/facets/core/facets/enumerable/accumulate.rb
lib/facets/core/facets/enumerable/take.rb
lib/facets/core/facets/enumerable/one.rb
lib/facets/core/facets/enumerable/cluster_by.rb
lib/facets/core/facets/enumerable/uniq_by.rb
lib/facets/core/facets/enumerable/occur.rb
lib/facets/core/facets/enumerable/map_with_index.rb
lib/facets/core/facets/enumerable/count.rb
lib/facets/core/facets/enumerable/map_by.rb
lib/facets/core/facets/enumerable/compact_map.rb
lib/facets/core/facets/enumerable/map_with.rb
lib/facets/core/facets/enumerable/exclude.rb
lib/facets/core/facets/enumerable/per.rb
lib/facets/core/facets/enumerable/group_by.rb
lib/facets/core/facets/enumerable/map_send.rb
lib/facets/core/facets/enumerable/modulate.rb
lib/facets/core/facets/enumerable/every.rb
lib/facets/core/facets/enumerable/none.rb
lib/facets/core/facets/enumerable/filter.rb
lib/facets/core/facets/enumerable/graph.rb
lib/facets/core/facets/enumerable/purge.rb
lib/facets/core/facets/enumerable/recursively.rb
lib/facets/core/facets/enumerable/each_with_object.rb
lib/facets/core/facets/to_hash.rb

Methods

Classes and Modules

Class Enumerable::Recursor

Public Instance methods

Accumulate a set of a set. For example, in an ORM design where `Group has_many User` we might have something equivalent to the following.

  Group = Struct.new(:users)
  User  = Struct.new(:name, :friends)

  user1 = User.new('John', [])
  user2 = User.new('Jane', ['Jill'])
  user3 = User.new('Joe' , ['Jack', 'Jim'])

  group1 = Group.new([user1, user2])
  group2 = Group.new([user2, user3])

  groups = [group1, group2]

Now we can accumulate the users of all groups.

  groups.accumulate.users  #=> [user1, user2, user3]

You may pass an argument to perform chains, e.g. the following returns the names of users from all groups.

  groups.accumulate(2).users.name  #=> ['John','Jane','Joe']

Or we can gather all the friends of all users in groups.

  groups.accumulate(2).users.friends  #=> ['Jill','Jack','Jim']

This is more convenient then the equivalent.

  groups.accumulate.users.accumulate.friends  #=> ['Jill','Jack','Jim']

CREDIT: George Moshchovitis, Daniel Emirikol

[Source]

# File lib/facets/core/facets/enumerable/accumulate.rb, line 40
  def accumulate(iterations=1)
    return self if iterations == 0
    Functor.new do |op, *args|
      result = inject([]) { |a, x| a << x.send(op, *args) }.flatten.uniq
      result.accumulate(iterations - 1)
    end
  end

Same as accumulate, but does not apply uniq to final result.

  groups.accumulate_all(2).users.friends  #=> ['Jill', 'Jill','Jack','Jim']

[Source]

# File lib/facets/core/facets/enumerable/accumulate.rb, line 52
  def accumulate_all(iterations=1)
    return self if iterations == 0
    Functor.new do |op, *args|
      result = inject([]) { |a, x| a << x.send(op, *args) }.flatten
      result.accumulate_all(iterations - 1)
    end
  end

Similar to group_by but returns an array of the groups. Returned elements are sorted by block.

   %w{this is a test}.cluster_by {|x| x[0]}
   #=> [ ['a'], ['is'], ['this', 'test'] ]

CREDIT: Erik Veenstra

[Source]

# File lib/facets/core/facets/enumerable/cluster_by.rb, line 13
  def cluster_by(&b)
    group_by(&b).sort.transpose.pop || []   # group_by(&b).values ?
  end
collect_with_index()

Alias for map_with_index

compact_collect(&block)

Alias for compact_map

A more versitle compact method. It can be used to collect and filter items out in one single step.

  c = [1,2,3].compact_map do |n|
    n < 2 ? nil : n
  end

  c  #=> [2,3]

CREDIT: Trans

DEPRECATE: This method should probably be removed b/c purge does almost the same thing and enum.map{}.compact works too.

[Source]

# File lib/facets/core/facets/enumerable/compact_map.rb, line 17
  def compact_map(&block)
    y = []
    if block_given?
      each do |*a|
        r = yield(*a)
        y << r unless r.nil?
      end
    else
      each do |r|
        y << r unless r.nil?
      end
    end
    y
  end

Count the number of items in an enumerable equal (==) to the given object(s).

  e = [ 'a', 1, 'a' ]

  e.count(1)       #=> 1
  e.count('a')     #=> 2

The method can count more than one item by supplying additional arguments.

  e.count('a', 1)  #=> 3

A block may also be used to select countable entries.

  e.count{ |x| String === x }  #=> 2

Note that Hash#count only considers values.

  e = { 'a' => 2, 'x' => 2, 'b' => 1 }

  e.count(1)  #=> 1
  e.count(2)  #=> 2

NOTE: This is one of the few method overrides in Facets.

CREDIT: Trans

[Source]

# File lib/facets/core/facets/enumerable/count.rb, line 33
  def count(*items, &block)
    if block || !items.empty?
      r = self
      r = r.select(&block) if block
      r = r.select{ |x| items.any?{ |i| i == x } } if !items.empty?
      r.size
    else
      begin
        size
      rescue
        i=0; each{ |e| i+=1 }; i
      end
    end
  end

Without a block: wrap the Enumerable object in such a way that map, select and similar operations are performed "horizontally" across a series of blocks, instead of building an array of results at each step. This reduces memory usage, allows partial results to be provided early, and permits working with infinite series.

  a = (1..1_000_000_000).defer.select{ |i| i % 2 == 0 }.
                               map{ |i| i + 100 }.
                               take(10).to_a

With a block: the block acts as an arbitrary filter on the data. Unlike map, it can choose to drop elements from the result, and/or add additional ones. The first object passed to the block is the receiver of the output.

  (1..1_000_000_000).
    defer { |out,i| out << i if i % 2 == 0 }.  # like select
    defer { |out,i| out << i + 100 }.          # like map
    take(10).to_a

Use a method like to_a or to_h at the end of the chain when you want an Array or Hash built with the results, or each{…} if you just want to output each result and discard it.

[Source]

# File lib/facets/core/facets/enumerable/defer.rb, line 29
  def defer(&blk)
    if block_given?
      Denumerator.new do |output|
        each do |*input|
          yield(output, *input)
        end
      end
    else
      Denumerator.new do |output|
        each do |*input|
          output.yield(*input)
        end
      end
    end
  end

Iterate through slices. If slice steps is not given, the arity of the block is used.

  x = []
  [1,2,3,4].each_by{ |a,b| x << [a,b] }
  x  #=> [ [1,2], [3,4] ]

  x = []
  [1,2,3,4,5,6].each_by(3){ |a| x << a }
  x  #=> [ [1,2,3], [4,5,6] ]

This is just like each_slice, except that it will check the arity of the block. If each_slice ever suppots this this method can be deprecated.

CREDIT: Trans

[Source]

# File lib/facets/core/facets/enumerable/each_by.rb, line 22
  def each_by(steps=nil, &block)
    if steps
      each_slice(steps, &block)
    else
      steps = block.arity.abs
      each_slice(steps, &block)
      #each_slice(steps) {|i| block.call(*i)}
    end
  end

A variation of inject that saves one from having to return the aggregate/memo argument.

Say we want to count characters in a string. Using the each_with_object method we have:

   "string".each_with_object(Hash.new(0)) do |c, h|
     h[c] += 1
   end

versus using inject which would be:

   "string".inject(Hash.new(0)) do |h, c|
     h[c] +=1
     h
   end

Notice that the order of the block parameters is reversed.

This method used be called injecting and had the same parameter order as inject, but Ruby 1.9 has adopted this method, so we support it instead.

[Source]

# File lib/facets/core/facets/enumerable/each_with_object.rb, line 28
    def each_with_object(memo) #:yield:
      each do |element|
        yield(element, memo)
      end
      memo
    end
elementwise(count=1)

Alias for ewise

Returns an elemental object. This allows you to map a method on to every element.

  r = [1,2,3].every + 3
  r  #=> [4,5,6]

[Source]

# File lib/facets/core/facets/enumerable/every.rb, line 11
  def every
    per(:map)
  end

In place version of every.

[Source]

# File lib/facets/core/facets/enumerable/every.rb, line 17
  def every!
    raise NoMethodError unless respond_to?(:map!)
    per(:map!)
  end

Returns an elementwise Functor designed to make R-like elementwise operations possible. This is very much like the every method, but it treats array argument specially.

  ([1,2].ewise + 3)          #=> [4,5]

Vector to vector

  ([1,2].ewise + [4,5])      #=> [5,7]

Special thanks to Martin DeMello for helping to develop this.

[Source]

# File lib/facets/core/facets/enumerable/ewise.rb, line 17
  def ewise(count=1)
    Functor.new do |op,*args|
      if args.empty?
        r = self
        count.times do
          r = r.collect{ |a| a.send(op) }
        end
        r
      else
        r = args.collect do |arg|
          if Array === arg #arg.kind_of?(Enumerable)
            x = self
            count.times do
              ln = (arg.length > length ? length : arg.length )
              x = x.slice(0...ln)
              x = x.zip(arg[0...ln])
              x = x.collect{ |a,b| a.send(op,b) }  #x = x.collect{ |a,b| b ? a.send(op,b) : nil }
            end
            x
          else
            x = self
            count.times do
              x = x.collect{ |a| a.send(op,arg) }
            end
            x
          end
        end
        r.flatten! if args.length == 1
        r
      end
    end
  end

The inverse of include?.

 [:a, :b].exclude?(:c)  #=> true
 [:a, :b].exclude?(:a)  #=> false

[Source]

# File lib/facets/core/facets/enumerable/exclude.rb, line 10
    def exclude?(object)
      !include?(object)
    end

Expand all elements of an Enumerable object.

  [0, 2..3, 5..7].expand  #=> [0,[2, 3],[5,6,7]]

CREDIT: Trans

[Source]

# File lib/facets/core/facets/enumerable/expand.rb, line 8
  def expand
    map do |x|
     (Enumerable === x ? x.expand : x)
    end
  end

The block acts as an arbitrary filter on the data. Unlike map, it can choose to drop elements from the result and/or add additional elements. The first object passed to the block is the receiver of the output.

  x = (1..10000)
  x = x.filter{ |out,i| out << i if i % 2 == 0 }   # like select
  x = x.filter{ |out,i| out << i + 100 }           # like map
  x = x.take(3)

  x  #=> [102, 104, 106]

This is very similar to each_with_object, but filter handles argument better by reversing their order and using the splat operator. (This was also once known as injecting.)

CREDIT: David Black, Louis J Scoras

[Source]

# File lib/facets/core/facets/enumerable/filter.rb, line 21
  def filter(output=[]) #:yeild:
    if block_given?
      each do |*input|
        yield(output, *input)
      end
      output
    else
      to_enum(:filter)
    end
  end

Yield each element to the block and return the result of the block when that result evaluates as true, terminating early like detect and find.

  obj1 = Object.new
  obj2 = Object.new

  def obj1.foo?; false; end
  def obj2.foo?; true ; end

  def obj1.foo ; "foo1"; end
  def obj2.foo ; "foo2"; end

  [obj1, obj2].find_yield{ |obj| obj.foo if obj.foo? }  #=> "foo2"

Another example.

  [1,2,3,4,5].find_yield{ |i| j = i+1; j if j % 4 == 0 }  #=> 4

If the block is never true, return the object given in the first parameter, or nil if none specified.

  [1,2,3].find_yield{ |_| false }    #=> nil
  [false].find_yield(1){ |_| false } #=> 1

[Source]

# File lib/facets/core/facets/enumerable/find_yield.rb, line 28
  def find_yield(fallback=nil) #:yield:
    each do |member|
      result = yield(member)
      return result if result 
    end
    fallback
  end

Generates a hash mapping each unique symbol in the array to the absolute frequency it appears.

  [:a,:a,:b,:c,:c,:c].frequency  #=> {:a=>2,:b=>1,:c=>3}

CREDIT: Brian Schröder

[Source]

# File lib/facets/core/facets/enumerable/frequency.rb, line 18
  def frequency
    p = Hash.new(0); each{ |v| p[v] += 1 }; p

  end

Like `map`/`collect`, but generates a Hash. The block is expected to return two values: the key and the value for the new hash.

  numbers  = (1..3)
  squares  = numbers.graph{ |n| [n, n*n] }   # { 1=>1, 2=>4, 3=>9 }
  sq_roots = numbers.graph{ |n| [n*n, n] }   # { 1=>1, 4=>2, 9=>3 }

CREDIT: Andrew Dudzik (adudzik), Trans

[Source]

# File lib/facets/core/facets/enumerable/graph.rb, line 12
  def graph(&yld)
    if yld
      h = {}
      each do |*kv|
        r = yld[*kv]
        case r
        when Hash
          nk, nv = *r.to_a[0]
        when Range
          nk, nv = r.first, r.last
        else
          nk, nv = *r
        end
        h[nk] = nv
      end
      h
    else
      Enumerator.new(self,:graph)
    end
  end

Enumerable#group_by is used to group items in a collection by something they have in common. The common factor is the key in the resulting hash, the array of like elements is the value.

  (1..5).group_by { |n| n % 3 }
  #=> { 0 => [3], 1 => [1, 4], 2 => [2,5] }

Applied to an array.

  ["I had", 1, "dollar and", 50, "cents"].group_by { |e| e.class }
  #=> { String => ["I had","dollar and","cents"], Fixnum => [1,50] }

Applied to a hash:

  {:a=>1, :b=>2, :c=>1}.group_by{ |k,v| v }
  #=> { 1=>[[:c,1], [:a,1]], 2=>[[:b,2]] }

CREDIT: Erik Veenstra

[Source]

# File lib/facets/core/facets/enumerable/group_by.rb, line 24
    def group_by #:yield:
      r = Hash.new
      each{ |e| (r[yield(e)] ||= []) << e }
      r
    end

Like group_by, but maps the second value returned from the block.

  a = [1,2,3,4,5]
  a.map_by{ |e| [e % 2, e + 1] }
  #=> { 0=>[3,5], 1=>[2,4,6] }

Works well with a hash too.

  h = {"A"=>1, "B"=>1, "C"=>1, "D"=>2, "E"=>2}
  h.map_by{ |k,v| [v, k.downcase] }
  #=> {1=>["a", "b", "c"], 2=>["d", "e"]}

If a second value is not returned, map_by acts like group_by.

  h = {"A"=>1, "B"=>1, "C"=>1, "D"=>2, "E"=>2}
  h.map_by{ |k,v| v }
  #=> {1=>[["A",1], ["B",1], ["C",1]], 2=>[["D",2], ["E",2]]}

[Source]

# File lib/facets/core/facets/enumerable/map_by.rb, line 21
  def map_by #:yield:
    res = {}
    each do |a|
      k,v = yield(*a)
      if v
        (res[k] ||= []) << v
      else
        (res[k] ||= []) << a
      end
    end
    res
  end
map_detect(fallback=nil)

Alias for find_yield

Send a message to each element and collect the result.

  [1,2,3].map_send(:+, 3)  #=> [4,5,6]

CREDIT: Sean O‘Halpin

[Source]

# File lib/facets/core/facets/enumerable/map_send.rb, line 9
  def map_send(meth, *args, &block)
    map{|e| e.send(meth, *args, &block)}
  end

Combines zip and map in a single efficient operation.

  h = {}
  [1,2,3].map_with [:x,:y,:z] do |n,k|
    h[k] = n
  end
  h  #=> {:x=>1, :y=>2, :z=>3}

[Source]

# File lib/facets/core/facets/enumerable/map_with.rb, line 11
  def map_with(*arrays, &block)
    enum_for(:zip, *arrays).map(&block)
  end

Same as collect but with an iteration counter.

  a = [1,2,3].collect_with_index { |e,i| e*i }
  a  #=> [0,2,6]

CREDIT: Gavin Sinclair

[Source]

# File lib/facets/core/facets/enumerable/map_with_index.rb, line 10
  def map_with_index
    r = []
    each_with_index do |e, i|
      r << yield(e, i)
    end
    r
  end
mash(&yld)

Alias for graph

Modulate. Divide an array into groups by modulo of the index.

  [2,4,6,8].modulate(2)  #=> [[2,6],[4,8]]

CREDIT: Trans

NOTE: Would the better name for this be ‘collate’?

[Source]

# File lib/facets/core/facets/enumerable/modulate.rb, line 11
  def modulate(modulo)
    return to_a if modulo == 1
    raise ArgumentError, 'bad modulo' if size % modulo != 0
    r = Array.new(modulo, [])
    (0...size).each do |i|
      r[i % modulo] += [self[i]]
    end
    r
  end

Enumerable#none? is the logical opposite of the builtin method Enumerable#any?. It returns true if and only if none of the elements in the collection satisfy the predicate.

If no predicate is provided, Enumerable#none? returns true if and only if none of the elements have a true value (i.e. not nil or false).

  [].none?                      # => true
  [nil].none?                   # => true
  [5,8,9].none?                 # => false
  (1...10).none? { |n| n < 0 }  # => true
  (1...10).none? { |n| n > 0 }  # => false

CREDIT: Gavin Sinclair

[Source]

# File lib/facets/core/facets/enumerable/none.rb, line 21
    def none?  # :yield: e
      if block_given?
        not self.any? { |e| yield e }
      else
        not self.any?
      end
    end

Returns an array of elements for the elements that occur n times. Or according to the results of a given block.

  a = [1,1,2,3,3,4,5,5]

  a.occur(1).sort               #=> [2,4]
  a.occur(2).sort               #=> [1,3,5]
  a.occur(3).sort               #=> []

  a.occur(1..1).sort            #=> [2,4]
  a.occur(2..3).sort            #=> [1,3,5]

  a.occur { |n| n == 1 }.sort   #=> [2,4]
  a.occur { |n| n > 1 }.sort    #=> [1,3,5]

[Source]

# File lib/facets/core/facets/enumerable/occur.rb, line 18
  def occur(n=nil) #:yield:
    result = Hash.new { |hash, key| hash[key] = Array.new }
    self.each do |item|
      key = item
      result[key] << item
    end
    if block_given?
      result.reject! { |key, values| ! yield(values.size) }
    else
      raise ArgumentError unless n
      if Range === n
        result.reject! { |key, values| ! n.include?(values.size) }
      else
        result.reject! { |key, values| values.size != n }
      end
    end
    return result.values.flatten.uniq
  end

Enumerable#one? returns true if and only if exactly one element in the collection satisfies the given predicate.

If no predicate is provided, Enumerable#one? returns true if and only if exactly one element has a true value (i.e. not nil or false).

  [].one?                      # => false
  [nil].one?                   # => false
  [5].one?                     # => true
  [5,8,9].one?                 # => false
  (1...10).one? { |n| n == 5 } # => true
  (1...10).one? { |n| n < 5 }  # => false

CREDIT: Gavin Sinclair

[Source]

# File lib/facets/core/facets/enumerable/one.rb, line 21
    def one?  # :yield: e
      matches = 0
      if block_given?
        self.each do |e|
          if yield(e)
            matches += 1
            return false if matches > 1
          end
        end
        return (matches == 1)
      else
        one? { |e| e }
      end
    end

Per element meta-functor.

  ([1,2,3].per(:map) + 3)     #=> [4,5,6]
  ([1,2,3].per(:select) > 1)  #=> [2,3]

Using fluid notation.

  ([1,2,3].per.map + 3)       #=> [4,5,6]
  ([1,2,3].per.select > 1)    #=> [2,3]

[Source]

# File lib/facets/core/facets/enumerable/per.rb, line 19
  def per(enum_method=nil, *enum_args)
    if enum_method
      Permeator.new(self, enum_method, *enum_args)
    else
      Functor.new do |enumr_method, *enumr_args|
        Permeator.new(self, enumr_method, *enumr_args)
      end
    end
  end

A versitle compaction method. Like map but used to filter out multiple items in a single step.

Without trash arguments nil is assumed.

  [1, nil, 2].purge  #=> [1,2]

If trash arguments are given, each argument is compared for a match using #==.

  (1..6).purge(3,4)  #=> [1,2,5,6]

If a block is given, the yield is used in the matching condition instead of the element itsef.

  (1..6).purge(0){ |n| n % 2 }  #=> [1,3,5]

NOTE: This could just as well be an override of the core compact method, but to avoid potential issues associated with overriding core methods we use the alternate name purge.

CREDIT: Trans

[Source]

# File lib/facets/core/facets/enumerable/purge.rb, line 27
  def purge(*trash, &block)
    trash = [nil] if trash.empty?
    r = []
    if block_given?
      each do |e|
        y = yield(e)
        r << e unless trash.any?{|t| t == y}
      end
    else
      each do |e|
        r << e unless trash.any?{|t| t == e}
      end
    end
    r
  end

Returns a recursive functor, that allows enumerable methods to iterate through enumerable sub-elements. By default it only recurses over elements of the same type.

[Source]

# File lib/facets/core/facets/enumerable/recursively.rb, line 7
  def recursively(*types, &block)
    Recursor.new(self, *types, &block)
  end

Uses #+ to sum the enumerated elements.

  [1,2,3].sum  #=> 6
  [3,3,3].sum  #=> 9

[Source]

# File lib/facets/core/facets/enumerable/sum.rb, line 8
  def sum(identity = 0, &block)
    if block_given?
      map(&block).sum
    else
      inject{ |sum, element| sum + element } || identity
    end
  end

Return the first n items from the collection

[Source]

# File lib/facets/core/facets/enumerable/take.rb, line 5
  def take(n)
    res = []
    count = 0
    each do |e|
      break if count >= n
      res << e
      count += 1
    end
    res
  end

Convert an Enumerable object into a hash by first turning it into an array.

CREDIT: Trans

[Source]

# File lib/facets/core/facets/to_hash.rb, line 227
  def to_h(mode=nil)
    to_a.to_h(mode)
  end

[Source]

# File lib/facets/core/facets/to_hash.rb, line 243
  def to_h_assoc
    to_a.to_h_assoc
  end

[Source]

# File lib/facets/core/facets/to_hash.rb, line 231
  def to_h_auto
    to_a.to_h_auto
  end

[Source]

# File lib/facets/core/facets/to_hash.rb, line 239
  def to_h_flat
    to_a.to_h_flat
  end

[Source]

# File lib/facets/core/facets/to_hash.rb, line 247
  def to_h_multi
    to_a.to_h_multi
  end

[Source]

# File lib/facets/core/facets/to_hash.rb, line 235
  def to_h_splat
    to_a.to_h_splat
  end

Like uniq, but determines uniqueness based on a given block.

  (-5..5).to_a.uniq_by {|i| i*i }
  #=> [-5, -4, -3, -2, -1, 0]

[Source]

# File lib/facets/core/facets/enumerable/uniq_by.rb, line 8
  def uniq_by #:yield:
    h = {}; inject([]) {|a,x| h[yield(x)] ||= a << x}
  end

Recursively iterate over all Enumerable elements, or subset given :type=>[type1, type2, …].

  [1, 2, 8..9].visit{ |x| x.succ }
  # => [2, 3, [9, 10]]

[Source]

# File lib/facets/core/facets/enumerable/visit.rb, line 9
  def visit(opts={}, &block)
    type = opts[:type] ? [opts[:type]].flatten : [Enumerable]
    skip = opts[:skip]

    map do |v|
      case v
      when String # b/c of 1.8
        block.call(v)
      when *type
        v.visit(opts, &block)
      else
        if skip && Enumerable === v
          v
        else
          block.call(v)
        end
      end
    end
  end
zip_map(*arrays, &block)

Alias for map_with

[Validate]