i have an array with sorted integers
array = [1,4,10,14,22]
i would like to create from array before an
array_with_ranges = [[0..1],[2..4],[5..10],[11..14],[15..22]]
i cant create a right iterator, i'm newbie in rails. In every ranges i have end_range value, but don't know how to set a start_range value? in most ranges in array_with_ranges the start_range is a end_range before +1 (except [0..1])
any solutions or ideas?
thank you for answers.
p.s.: happy new 2015 year
Add a helper value of -1, later on remove it.
array = [1,4,10,14,22]
array.unshift(-1)
ranges = array.each_cons(2).map{|a,b| a+1..b} #=>[0..1, 2..4, 5..10, 11..14, 15..22]
array.shift
You can iterate on all elements of the array and save the previous value in the external variable, like this:
last = -1
array.collect {|x| prev = last; last = x; (prev+1..x)}
Just keeping track of the previous value takes care of it:
2.1.5 :001 > array = [1,4,10,14,22]
=> [1, 4, 10, 14, 22]
2.1.5 :002 > previous = 0
=> 0
2.1.5 :003 > array.map { |i| rng = previous..i; previous = i + 1; rng }
=> [0..1, 2..4, 5..10, 11..14, 15..22]
I imagine there's a slicker way to do it though.
edit: Of course there is, building on @steenslag's answer:
2.1.5 :001 > array = [1, 4, 10, 14, 22]
=> [1, 4, 10, 14, 22]
2.1.5 :002 > ([-1] + array).each_cons(2).map { |a,b| (a + 1)..b }
=> [0..1, 2..4, 5..10, 11..14, 15..22]
