Range

The syntax to define a range is a..b, with a and b non-negative integers, e.g. 2..10.

Both a and b might also be omitted - in that case the range becomes open.

According to the amount of delimiters provided, a range can be classified as:

• Closed range: a..b
• Open on the left end: ..b
• Open on the right end: a..
• Open on both ends: ..

The behavior of open ranges is not universally defined, but rather defined by each function that accepts a range: see .read as an example, whose strategy is common for slicing operations across the stdlib.

 

The .. operator is syntactic sugar for the .range {from} {to} function, with the difference that the first accepts only literal values. When the ends of the range need to be evaluated dynamically, such as through a mathematical operation, .range is the appropriate choice.