“Show all posts from newest to oldest” is an algorithm.
“Shows random 10 posts, unordered” is an algorithm.
It’s not possible to show a list of items without an algorithm. You may of course take issue with what the algorithm is, but you can’t not have one.
It’s a shorthand for writing this:
variable = if (input != null) input else default
This is equivalent:
variable = input ?: default
The answers confusing it with the ternary operator are wrong.
Because it’s not one. Ternary operator is A ? B : C, Elvis operator is A ?: B. The same two characters are involved, but both the syntax and effect is different.
It’s a shorthand for writing this:
variable = if (input != null) input else defaultThis is equivalent:
variable = input ?: default