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qbyt/comprehension.rb

Created September 6, 2013 09:37
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comprehension.rb
class Proc
def self.compose(f, g)
lambda { |*args| f[g[*args]] }
end
def *(g)
Proc.compose(self, g)
end
end
def comprehension(range, mappers = [], filters = [])
mappers = mappers.reduce(:*)
filters = filters
filtered = range.reduce([]) do |accum, val|
inc = filters.map do |filter|
filter[val]
end.all?
inc ? accum << val : accum
end
filtered.map { |x| mappers[x] }
end
# list comprehension
comprehension(1..10, [->(x) { x / 2 }, ->(y) { y ** y }], [->(z) { z.odd? }])
# set comprehension
Set.new(comprehension(1..10, [->(x) { x / 2 }, ->(y) { y ** y }], [->(z) { z.odd? }]))
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