I have an array that looks like this:
Array_1 = ["A1", "A2", "A3", "A4", "A5", "B1", "B2", "B3", ..., "Z5"]
I want to create another array with the elements of Array_1 that come after "A5":
Array_2 = ["B1", "B2", "B3", ..., "Z5"]
I have an ugly way that subtracts two arrays to create a third array, but I feel like there is bound to be a classy ruby way of doing something that should be simple. Any help would be amazeballs.
Array_1 = ["A1", "A2", "A3", "A4", "A5", "B1", "B2", "B3", "Z5"]
Array_1[Array_1.index("A5")+1..-1]
# => ["B1", "B2", "B3", "Z5"]
(I suppose we should first compute idx = Array_1.index("A5") to make sure it's non-nil.)
. . .
Another way makes use of Ruby's little-used flip-flop operator:
Array_1.select { |e| e=="A5" .. false ? true : false }[1..-1]
#=> ["B1", "B2", "B3", "Z5"]
The expression remains false until e=="A5" is true, and remains true until the expression following the two dots is true. Therefore,
Array_1.select { |e| e=="A5" .. false ? true : false }
#=> ["A5", "B1", "B2", "B3", "Z5"]
[1..-1] is tacked on to return this array without "A5".
The flip-flop operator must be part of a conditional expression, which is why we cannot write:
Array_1.select { |e| e=="A5" .. false }[1..-1]
#ArgumentError: bad value for range
(for e=="A5" .. false is treated as a normal range).
Array_1.slice_when{|e| e == "A5"}.to_a.last
# => ["B1", "B2", "B3", ..., "Z5"]
How about this?
arr = ["A1", "A2", "A3", "A4", "A5", "B1", "B2", "B3", "Z5"]
p arr.drop_while {|s| s != "A5" }.drop(1)
# => ["B1", "B2", "B3", "Z5"]
.slice_after takes an argument for slicing array
Array_1.slice_after("A5").to_a.last
=> ["B1", "B2", "B3", "Z5"]
This creates the array that your are using using a regex match.
array = ('A1'..'Z5').to_a.reject { |el| el.match %r/[A-Z][0, 6-9]/ }
Then to remove the "A(digit)" elements using another regex match.
array_2 = array.select { |el| el.match %r/[B-Z]\d/ }
This has the added benefit of not caring about order, and can separate them regardless.
