Created
July 4, 2012 12:00
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Some class that may be useful for dealing with time ranges.
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# This class assumes that you have ranges associated to a value | |
# and that you want to merge those values. This is, for instance, | |
# useful to count overlaps of date ranges. | |
# | |
# Example of uses: | |
# | |
# rm = RangeMixer.new(0..10, 0) | |
# rm.add(0..5){ |memo| memo + 1 } | |
# rm.add(0..5){ |memo| memo + 4 } | |
# | |
# puts rm.hash.inspect # => {0=>5, 5=>4, 7=>0} | |
# | |
# The previous example can also be written as: | |
# | |
# rm = RangeMixer.new(0..10, 0){ |memo, value| memo + value } | |
# rm.add(0..5, 1) | |
# rm.add(0..7, 4) | |
# | |
# The last method avoid the creation of useless Proc objects. | |
# | |
# This is an other context (where ActiveSupport is required): | |
# | |
# from = Date.today ; to = from + 1.month | |
# rm = RangeMixer.new(from..to, 0){ |memo, _| memo + 1 } | |
# rm.add(from..(from + 1.week)) | |
# rm.add((from + 1.week)..to) | |
# | |
# # Check if there is an overlap | |
# rm.hash.values.any?{ |v| v > 1 } # => false | |
# | |
# rm.add((from + 3.days)..to) | |
# | |
# # Check if there is an overlap | |
# rm.hash.values.any?{ |v| v > 1 } # => true | |
class RangeMixer | |
attr_reader :hash | |
def initialize(range, memo, &mixer) | |
@start = range.begin | |
@stop = range.end | |
@memo = memo | |
@mixer = mixer | |
@hash = {@start => @memo} | |
end | |
def add(range, value=nil, &block) | |
return if range.end <= @start || range.begin >= @stop | |
insert_steps!(range) | |
fill_steps!(range, value || block) | |
end | |
private | |
def fill_steps!(range, pv) | |
@hash.each do |step, memo| | |
if range.begin <= step && step < range.end | |
@hash[step] = pv.kind_of?(Proc) ? pv.call(memo) : @mixer.call(memo, pv) | |
end | |
end | |
@hash | |
end | |
def insert_steps!(range) | |
@hash[range.begin] ||= previous(range.begin) if range.begin > @start | |
@hash[range.end] ||= previous(range.end) if range.end < @stop | |
end | |
def previous(step) | |
prev = @start | |
@hash.keys.sort.find{ |d| if d > step then true else prev = d and false end } | |
@hash[prev] | |
end | |
end |
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