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.
Returns an array of the first element upto, but not including, the last element.
[1,2,3].body #=> [1,2]
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# File lib/core/facets/indexable.rb, line 71 def body slice(0,size-1) end
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+.
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# File lib/core/facets/indexable.rb, line 192 def ends return nil if size == 0 size - 1 end
Returns first n elements.
"Hello World".first(3) #=> "Hel"
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# File lib/core/facets/indexable.rb, line 130 def first(n=1) slice(0, n.to_i) end
Remove and return the first element.
a = [1,2,3] a.first! #=> 1 a #=> [2,3]
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# File lib/core/facets/indexable.rb, line 170 def first! splice(0) end
Change the first element.
a = ["a","y","z"] a.first = "x" p a #=> ["x","y","z"]
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# File lib/core/facets/indexable.rb, line 150 def first=(x) splice(0,x) end
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# File lib/core/facets/indexable.rb, line 58 def foot slice(-1,1) end
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# File lib/core/facets/indexable.rb, line 41 def head slice(0,1) end
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
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# 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
Alias for index
Returns last n elements.
"Hello World".last(3) #=> "rld"
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# 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
Remove and return the last element.
a = [1,2,3] a.last! #=> 3 a #=> [1,2]
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# File lib/core/facets/indexable.rb, line 180 def last! splice(-1) end
Change the last element.
a = [1,2,5] a.last = 3 p a #=> [1,2,3]
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# File lib/core/facets/indexable.rb, line 160 def last=(x) splice(-1,x) end
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).
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# File lib/core/facets/indexable.rb, line 89 def mid(offset=0) slice((size / 2) + offset) end
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.
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# 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
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
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# File lib/core/facets/indexable.rb, line 203 def pos(i) if i > 0 return i - 1 else size + i end end
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
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# 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