Indexable

Indexable is a mixin that provides index based methods, working soley with four methods: index, slice, splice and size.

These methods work in harmony. Where index returns a position of a given element, slice returns elements for given positions. splice is like slice but replaces the given position with new values. This mehtod is not part of ruby core, but it generally just an alias for #[]=, just as slice is an alias of #[]. size of course simply returns the total length of the indexable object.

Methods
body ends first first! first= foot head index index_of last last! last= mid middle pos range tail thru
Public Instance methods
body()

Returns an array of the first element upto, but not including, the last element.

  [1,2,3].body  #=> [1,2]
# File lib/core/facets/indexable.rb, line 71
  def body
    slice(0,size-1)
  end
ends()

A shorting of "ends at", returns the last index of the indexable object. Returns nil if there are no elements.

  [1,2,3,4,5].ends  #=> 4

This nearly equivalent to +size - 1+.

# File lib/core/facets/indexable.rb, line 192
  def ends
    return nil if size == 0
    size - 1
  end
first(n=1)

Returns first n elements.

  "Hello World".first(3)  #=> "Hel"
# File lib/core/facets/indexable.rb, line 130
  def first(n=1)
    slice(0, n.to_i)
  end
first!()

Remove and return the first element.

  a = [1,2,3]
  a.first!      #=> 1
  a             #=> [2,3]
# File lib/core/facets/indexable.rb, line 170
  def first!
    splice(0)
  end
first=(x)

Change the first element.

  a = ["a","y","z"]
  a.first = "x"
  p a           #=> ["x","y","z"]
# File lib/core/facets/indexable.rb, line 150
  def first=(x)
    splice(0,x)
  end
foot()

Like last, returning the last element in an array.

  [1,2,3].foot  #=> [3]
# File lib/core/facets/indexable.rb, line 58
  def foot
    slice(-1,1)
  end
head()

Like first but returns the first element in a new array.

  [1,2,3].head  #=> [1]
# File lib/core/facets/indexable.rb, line 41
  def head
    slice(0,1)
  end
index(obj=nil) {|slice(i)| ...}

Returns the index of the first element equal to the given object or satisfying the block condition.

  [1,2,3,4].index{ |e| e == 3 }  #=> 2
  [1,2,3,4].index{ |e| e > 3 }   #=> 3
This method is also aliased as index_of
# File lib/core/facets/indexable.rb, line 217
  def index(obj=nil, &block)
    if block_given?
      size.times do |i|
        return i if yield(slice(i))
      end
    else
      size.times do |i|
        return i if obj == slice(i)
      end
    end
    nil
  end
index_of(obj=nil, &block)

Alias for index

last(n=1)

Returns last n elements.

  "Hello World".last(3)  #=> "rld"
# File lib/core/facets/indexable.rb, line 138
  def last(n=1)
    n = n.to_i
    return self if n > size
    slice(-n, n) #slice(-n..-1)
  end
last!()

Remove and return the last element.

  a = [1,2,3]
  a.last!       #=> 3
  a             #=> [1,2]
# File lib/core/facets/indexable.rb, line 180
  def last!
    splice(-1)
  end
last=(x)

Change the last element.

  a = [1,2,5]
  a.last = 3
  p a           #=> [1,2,3]
# File lib/core/facets/indexable.rb, line 160
  def last=(x)
    splice(-1,x)
  end
mid(offset=0)

Returns the middle element of an array, or the element offset from middle if the parameter is given. Even-sized arrays, not having an exact middle, return the middle-right element.

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

In other words, If there are an even number of elements the higher-indexed of the two center elements is indexed as orgin (0).

# File lib/core/facets/indexable.rb, line 89
  def mid(offset=0)
    slice((size / 2) + offset)
  end
middle()

Returns the middle element(s) of an array. Even-sized arrays, not having an exact middle, returns a two-element array of the two middle elements.

  [1,2,3,4,5].middle        #=> 3
  [1,2,3,4,5,6].middle      #=> [3,4]

In contrast to mid which utilizes an offset.

# File lib/core/facets/indexable.rb, line 102
  def middle
    if size % 2 == 0
     slice( (size / 2) - 1, 2 )
     #[slice((size / 2) - 1, 1), slice(size / 2, 1)]
    else
      slice(size / 2)
    end
  end
pos(i)

Returns the positive ordinal index given a cardinal position, 1 to n or -n to -1.

  [1,2,3,4,5].pos(1)   #=> 0
  [1,2,3,4,5].pos(-1)  #=> 4
# File lib/core/facets/indexable.rb, line 203
  def pos(i)
    if i > 0
      return i - 1
    else
      size + i
    end
  end
range(a=nil,z=nil)

Returns the index range between two elements. If no elements are given, returns the range from first to last.

  ['a','b','c','d'].range            #=> 0..3
  ['a','b','c','d'].range('b','d')   #=> 1..2
# File lib/core/facets/indexable.rb, line 242
  def range(a=nil,z=nil)
    if !a
      0..(size-1)
    else
      index(a)..index(z)
    end
  end
tail()

Returns an array from second element to last element.

  [1,2,3].tail  #=> [2,3]
# File lib/core/facets/indexable.rb, line 49
  def tail
    slice(1,length-1)
  end
thru(from, to)

Fetch values from a start index thru an end index.

  [1,2,3,4,5].thru(0,2)  #=> [1,2,3]
  [1,2,3,4,5].thru(2,4)  #=> [3,4,5]
# File lib/core/facets/indexable.rb, line 116
  def thru(from, to)
    a = []
    i = from
    while i <= to
      a << slice(i)
      i += 1
    end
    a
  end