There are two range expressions:
- Defined ranges
- Undefined ranges
Defined ranges
Defined ranges represent a group of values that are generated as a sequence based on some predefined rules. Ranges are represented with two dots .. operator.
{ 1..8 } // a range from 1 to 8
{ 1,2,3,4,5,6,7,8 }
{ 8..1 } // a range from 8 to 1
{ 8,7,6,5,4,3,2,1 }
{ 1..8..2 } // a range from 1 to 8 jumping by 2
{ 1,3,5,7 }
{ 3..-3 } // a range from 4 to -4
{ 3,2,1,0,-1,-2,-3 }
{ -3..3 } // a range from -3 to 3
{ -3,-2,-1,0,1,2,3 }
{ ..5 } // a range form 0 to 5
{ 0,1,2,3,4,5 }
{ ..-5 } // a range from 0 to -5
{ 0,-1,-2,-3,-4,-5 }
{ 5.. } // a range from 5 to 0
{ 5,4,3,2,1,0 }
{ -5.. } // a range from -5 to 0
{ -5,-4,-3,-2,-1,0 }
| syntax | meaning |
|---|---|
start..end |
from start to end |
..end |
from zero to end |
start.. |
from start to zero |
Undefined ranges
Undefined ranges represent values that have only one side defined at the definition time, and the compiler defines the other side at compile time. They are represented with three dots ...
{ 2... } // from 2 to infinity
| syntax | meaning |
|---|---|
start... |
from start to infinite |
In most of the cases, they are used for variadic parameters passing:
fun calc(number: ...int): int = { return number[0] + number[1] + number[2] * number[3]}