Range Type
The range type is used to represent sequences with a fixed step size. It is a generic type denoted as Range. When T is instantiated with different types, the type must support relational operators and be capable of addition with values of type Int64, resulting in different range types. For example, the most commonly used Range represents integer ranges.
Each instance of a range type contains three values: start, end, and step. Here, start and end represent the initial and terminal values of the sequence, respectively, while step denotes the difference between consecutive elements (i.e., the step size). The types of start and end are the same (i.e., the type with which T is instantiated), whereas step is of type Int64 and cannot be equal to 0.
The following example demonstrates how to instantiate range types (for details on range type definitions and their properties, refer to the Cangjie Programming Language Library API):
// Range<T>(start: T, end: T, step: Int64, hasStart: Bool, hasEnd: Bool, isClosed: Bool)
let r1 = Range<Int64>(0, 10, 1, true, true, true) // r1 contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
let r2 = Range<Int64>(0, 10, 1, true, true, false) // r2 contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
let r3 = Range<Int64>(10, 0, -2, true, true, false) // r3 contains 10, 8, 6, 4, 2Range Type Literals
Range literals come in two forms: "left-closed right-open" and "left-closed right-closed" ranges.
- The "left-closed right-open" range is formatted as start..end : step, representing a range that starts at start, increments by step, and ends before end (excluding end).
- The "left-closed right-closed" range is formatted as start..=end : step, representing a range that starts at start, increments by step, and includes end (including end).
The following example defines several range-type variables:
In range literals, step can be omitted, in which case it defaults to 1. However, the value of step cannot be 0. Additionally, a range may be empty (i.e., a sequence containing no elements), as shown below:
> Note:
>
> - For the expression start..end : step, when step > 0 and start >= end, or when step < 0 and start <= end, start..end : step is an empty range.
> - For the expression start..=end : step, when step > 0 and start > end, or when step < 0 and start < end, start..=end : step is an empty range.
let n = 10
let r1 = 0..10 : 1 // r1 contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
let r2 = 0..=n : 1 // r2 contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
let r3 = n..0 : -2 // r3 contains 10, 8, 6, 4, 2
let r4 = 10..=0 : -2 // r4 contains 10, 8, 6, 4, 2, 0let r5 = 0..10 // the step of r5 is 1, and r5 contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
let r6 = 0..10 : 0 // Error, step cannot be 0
let r7 = 10..0 : 1 // r7 to r10 are empty ranges
let r8 = 0..10 : -1
let r9 = 10..=0 : 1
let r10 = 0..=10 : -1