module Indexable

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.

Public Instance Methods

body() click to toggle source

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() click to toggle source

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) click to toggle source

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!() click to toggle source

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) click to toggle source

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() click to toggle source

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() click to toggle source

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)| ... } click to toggle source

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
# 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
Also aliased as: index_of
index_of(obj=nil, &block)

to be deprecated

Alias for: index
last(n=1) click to toggle source

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!() click to toggle source

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) click to toggle source

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) click to toggle source

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() click to toggle source

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) click to toggle source

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) click to toggle source

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() click to toggle source

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) click to toggle source

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