Ruby - Array Array Indexing
Introduction
You can index from the end of an array using negative numbers, where -1 is the index of the last element, -2 is the second-to-last, and so on.
You can also use ranges, like this:
Demo
arr = ['h','e','l','l','o',' ','w','o','r','l','d'] print( arr[0,5] ) #=> hello (or) ["h", "e", "l", "l", "o"] print( arr[-5,5 ] ) #=> world (or) ["w", "o", "r", "l", "d"] print( arr[0..4] ) #=> hello (or) ["h", "e", "l", "l", "o"] print( arr[-5..-1] ) #=> world (or) ["w", "o", "r", "l", "d"] # w ww .j a va2s . c o m
Result
If you use p instead of print to inspect the array, both Ruby 1.8 and 1.9 display the same result:
Demo
arr = ['h','e','l','l','o',' ','w','o','r','l','d'] p( arr[0,5] ) #=> ["h", "e", "l", "l", "o"] p( arr[0..4] ) #=> ["h", "e", "l", "l", "o"] # from w w w .ja v a 2 s.c om
Result
When you provide two integers in order to return a number of contiguous items from an array, the first integer is the start index, while the second is a count of the number of items ( not an index):
Demo
arr = ['h','e','l','l','o',' ','w','o','r','l','d'] p arr[0,5] # returns 5 chars - ["h", "e", "l", "l", "o"]
Result
