Ruby syntax for working with arrays (cheat-sheet):
| symbol | label | what it does |
|---|---|---|
| , | comma | for indexing array by: index, length |
| .. | two dots | inclusive range |
| … | three dots | non-inclusive range (doesn’t include last index) |
| + | plus | concatenate two arrays |
| – | minus | subtract two arrays |
| << | two less than | append to end of array |
| & | ampersand | union of two arrays |
| | | pipe | intersection of two arrays |
Some examples showing use of this:
| Example | Explanation | What you get |
|---|---|---|
| [‘a’] << ['b','c'] | append to end of array | [‘a’,’b’,’c’] |
| [1,1,2,2,3] | [1,2,3,4] | union of two arrays, duplicates are removed | [1,2,3,4] |
| [1,2,3] & [2,3,4] | intersection of two arrays | [2,3] |
| a[0..-1] | All but last element of array. (Note non-inclusive range … ) | |
| [1,2,3,4,5] | basic syntax array | [1,2,3] |
| [1…5] | non-inclusive range | [1,2,3,4] |
| a = [1..5] | inclusive range | [1,2,3,4,5] |
| a[0] | the first element of the array | 1 |
| a[-1] | another way to get the last element of the array | 5 |
| a[1,3] | starting index & number of elements | [2,3,4] |
| a = [1,2,3] + [4,5] | concatenate two arrays | [1,2,3,4,5] |
| [‘a’, ‘b’, ‘c’, ‘d’, ‘a’] – [‘b’, ‘c’] | subtracts one array from another | [‘a’, ‘d’] |
Some more examples. Assume for each example that a = [“a”, “b”, “c”, “d”, “e”]
| a[0…-1] | All but last element of array. (Note non-inclusive range … ) |
| a[0..-1] | Everything in the array. (Note inclusive range .. ) |
| a[1..-1] | All but first element of array. |