Ruby '..' aka "2 dot" range operator is inclusive, '...' aka "3 dot" range operator is exclusive

Pontifications

Ranges constructed using .. run from the beginning to the end inclusively. Those created using … exclude the end value.
It’s not like C! variable[0,n] is the same as ruby’s variable[0..n]. In ruby variable[x,n] means starting at position x, return n elements. Learned this the hard way in production-test-797-redirects.rb

#using ranges. The end position is included with two periods but not with three
array_four[0..1]              # => ["a", "b"]
array_four[0...1]             # => ["a"]