Ruby Programming Language :: Range comparisons


	Range comparisons Something came up as I was testing some ideas. I know Range objects can indicate whether a specific object is an included element, but something I thought might work didn't: irb(main):001:0> (1..10).include?(2..6) => false I know a simple case like this can be covered with (1..10).include? 2 and (1..10).include? 6 (range1 includes both range2.first and range2.last), but doing it that way seems not entirely right, especially when it comes to other cases. A big problem, as I see it, would be trying to figure out what to do if the second range excludes its end. Maybe I'm just thinking about this completely wrong. Maybe I should be using Sets or something. Knowing about intersects would be nice, too. Any thoughts? -- -yossef Here is an interesting discussion. http://opensoul.org/2007/2/13/ranges-include-or-overlap-with-ranges Anyway, nothing that would require more than 10 lines of code. On 04.06.2007 17:56, Yossef Mendelssohn wrote: - Hide quoted text - > Something came up as I was testing some ideas. I know Range objects > can indicate whether a specific object is an included element, but > something I thought might work didn't: > irb(main):001:0> (1..10).include?(2..6) > => false > I know a simple case like this can be covered with (1..10).include? 2 > and (1..10).include? 6 (range1 includes both range2.first and > range2.last), but doing it that way seems not entirely right, > especially when it comes to other cases. A big problem, as I see it, > would be trying to figure out what to do if the second range excludes > its end. > Maybe I'm just thinking about this completely wrong. Maybe I should > be using Sets or something. Knowing about intersects would be nice, > too. > Any thoughts? Similar discussions have come up here before. The net was, that because of all sorts of issues (which you partly identified yourself already) it would not be wise to extend functionality of Range#include? beyond the current behavior. You'll sure find more detail in the archives but one reason for example is that other Enumerable's include? methods always check for single element membership only. For all the other operations there is - and & etc. 18:13:10 [contentreporter]: irb -r set irb(main):001:0> s1=(1..10).to_set => #<Set: {5, 6, 1, 7, 2, 8, 3, 9, 4, 10}> irb(main):002:0> s2=(1...10).to_set => #<Set: {5, 6, 1, 7, 2, 8, 3, 9, 4}> irb(main):003:0> s1 == s2 => false irb(main):004:0> s1 - s2 => #<Set: {10}> irb(main):005:0> s2 - s1 => #<Set: {}> irb(main):010:0> s2.superset? s1 => false irb(main):011:0> s1.superset? s2 => true Kind regards robert Thanks to both of you (CHubas and Robert). I didn't see the replies because either I don't get replies to my threads e-mailed to me or I'm just oblivious. I've written a few things myself, things on the order of Range#contains?, Range#contained_by?, Range#overlaps?. The real trick, however comes when I'm using extensions built on top of Range, extensions that allow a range-ish objects that have open ends. I'm not talking about excluding the end, like 1...10, but allowing the absence of an end, like 1..nil. Now, that can be done easily enough with numbers and Infinity (1.0/0), but it gets troublesome when using, say, Times or Dates. -- -yossef