116 lines
2.2 KiB
Ruby
116 lines
2.2 KiB
Ruby
#
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# This Module was developed by Thomas Hafner.
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# No other references about the author.
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#
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# TITLE:
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#
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# Cartesian
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#
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# SUMMARY:
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#
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# Cartesian product and similar methods.
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#
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# AUTHORS:
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#
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# - Thomas Hafner
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#
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module Enumerable
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class << self
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# Provides the cross-product of two or more Enumerables.
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# This is the class-level method. The instance method
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# calls on this.
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#
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# Enumerable.cart([1,2], [4], ["apple", "banana"])
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# #=> [[1, 4, "apple"], [1, 4, "banana"], [2, 4, "apple"], [2, 4, "banana"]]
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#
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# Enumerable.cart([1,2], [3,4])
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# #=> [[1, 3], [1, 4], [2, 3], [2, 4]]
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def cartesian_product(*enums, &block)
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result = [[]]
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while [] != enums
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t, result = result, []
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b, *enums = enums
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t.each do |a|
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b.each do |n|
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result << a + [n]
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end
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end
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end
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if block_given?
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result.each{ |e| block.call(e) }
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else
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result
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end
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end
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alias_method :cart, :cartesian_product
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end
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# The instance level version of <tt>Enumerable::cartesian_product</tt>.
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#
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# a = []
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# [1,2].cart([4,5]){|elem| a << elem }
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# a #=> [[1, 4],[1, 5],[2, 4],[2, 5]]
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def cartesian_product(*enums, &block)
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Enumerable.cartesian_product(self, *enums, &block)
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end
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alias :cart :cartesian_product
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# Operator alias for cross-product.
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#
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# a = [1,2] ** [4,5]
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# a #=> [[1, 4],[1, 5],[2, 4],[2, 5]]
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#
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def **(enum)
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Enumerable.cartesian_product(self, enum)
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end
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# Expected to be an enumeration of arrays. This method
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# iterates through combinations of each in position.
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#
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# a = [ [0,1], [2,3] ]
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# a.each_combo { |c| p c }
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#
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# produces
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#
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# [0, 2]
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# [0, 3]
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# [1, 2]
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# [1, 3]
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#
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def each_combo
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a = collect{ |x|
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x.respond_to?(:to_a) ? x.to_a : 0..x
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}
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if a.size == 1
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r = a.shift
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r.each{ |n|
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yield n
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}
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else
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r = a.shift
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r.each{ |n|
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a.each_combo{ |s|
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yield [n, *s]
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}
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}
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end
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end
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# As with each_combo but returns combos collected in an array.
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#
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def combos
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a = []
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each_combo{ |c| a << c }
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a
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end
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end
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