class Range

Overview

class Range

The class of Range shows a range between begin and end. The object is created by new Range as below.

new Range(begin, end, excludingEnd)

dot style

The instance of class Range is also created by the dot style syntax as below.

There are 2 styles of .. and .... The style of .. means to include the end, but the style of ... means to exclude the end.

var a = 2..10;  // new Range(2, 10)
var b = 2...10; // new Range(2, 10, true)

Interfaces

The class Range have following methods.

Name	Outline
`begin()`	The value of the beginning point.
`end()`	The value of the end point. If you put nothing, returns `null`. This do not care about the `excludeEnd` flag.
`next()`	Returns the next value. If it is called a first time, the beginning value will be returned.
`isEndExcluded()`	`true` if the `Range` excludes the end.
`each([func])`	Iterates the range with callback to `func`.

Note that in each(func) with no end point, it will be an infinite loop.

Range as an index

Range object can be used as an index for Array, String, Binary, or Range like this.

a[2..3] // The variable `a` can be Array, String, Binary, or Range.
        // This means to return a set of elements from 2nd element to 3rd element.

Mechanism

The object used at the begin and end point of the class Range must have followings.

The operator <=>.
- It is used when comparing with the begin and end point.
The method named as next().
- It is used when iterating the object.

Restriction

The style of omitting the end point like n.. is available.

But currently you can NOT omit the beginning value because it causes a conflict with the spread/rest operator of .... If you need this, you can use the workaround with null as below.

a = null..10;   // no beginning point of Range.

Examples

Example 1. Normal case

Code

System.println((2..10).toArray());

Result

[2, 3, 4, 5, 6, 7, 8, 9, 10]

Example 2. With variable/expression

Code

You can use a variable or expression.

function makeRange(begin, len) {
    return begin..(begin+len);
}
System.println(makeRange(100, 2).end()); // => 102

Result

Example 3. String

Code

var a = "a".."z";     // new Range("a", "z")
var b = "ab"..."ax";  // new Range("ab", "ax", true)
System.println(a.toArray());
System.println(b.toArray());

Result

["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
["ab", "ac", "ad", "ae", "af", "ag", "ah", "ai", "aj", "ak", "al", "am", "an", "ao", "ap", "aq", "ar", "as", "at", "au", "av", "aw"]

Example 4. DateTime

Code

using DateTime;
for (var dt in DateTime(2000, 1, 1)..DateTime(2000, 1, 10)) {
    System.println(dt);
}

Result

2000/01/01 00:00:00
2000/01/02 00:00:00
2000/01/03 00:00:00
2000/01/04 00:00:00
2000/01/05 00:00:00
2000/01/06 00:00:00
2000/01/07 00:00:00
2000/01/08 00:00:00
2000/01/09 00:00:00
2000/01/10 00:00:00

Example 5. Range for Switch-Case (1)

Code

for (var i = 0; i <= 10; ++i) {
    switch (i) {
    case 1..4:
        System.println("okay 1 (%{i})");
        break;
    case 7...9:
        System.println("okay 2 (%{i})");
        break;
    default:
        System.println("out of range (%{i})");
        break;
    }
}

Result

out of range (0)
okay 1 (1)
okay 1 (2)
okay 1 (3)
okay 1 (4)
out of range (5)
out of range (6)
okay 2 (7)
okay 2 (8)
out of range (9)
out of range (10)

Example 6. Range for Switch-Case (2)

Code

for (var i in 'o'..'af') {
    switch (i) {
    case 'ac'..'ae':
        System.println("okay 1 (%{i})");
        break;
    case 'p'...'w':
        System.println("okay 2 (%{i})");
        break;
    default:
        System.println("out of range (%{i})");
        break;
    }
}

Result

out of range (o)
okay 2 (p)
okay 2 (q)
okay 2 (r)
okay 2 (s)
okay 2 (t)
okay 2 (u)
okay 2 (v)
out of range (w)
out of range (x)
out of range (y)
out of range (z)
out of range (aa)
out of range (ab)
okay 1 (ac)
okay 1 (ad)
okay 1 (ae)
out of range (af)

Example 7. Range for String

Range for String means to return a part of string between the start and the end of Range. It is like String#subString() but note that String#subString() requires a length.

Code

var str = "abcdefghijklmnopqrstuvwxyz";
System.println(str[2..25]);            // "cdefghijklmnopqrstuvwxyz"
System.println(str[2...25]);           // "cdefghijklmnopqrstuvwxy"
System.println(str.subString(2, 23));  // "cdefghijklmnopqrstuvwxy"

Result

cdefghijklmnopqrstuvwxyz
cdefghijklmnopqrstuvwxy
cdefghijklmnopqrstuvwxy

Example 8. Range for Array

Range for Array means to return a part of array between the start and the end of Range. It is like Array#subArray() but note that Array#subArray() requires a length.

Code

var ary = 16.times();
System.println(ary[2..12]);            // [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
System.println(ary[2...12]);           // [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
System.println(ary.subArray(2, 10));   // [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

Result

[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

Example 9. Range for Binary

Range for Binary means to return a part of binary between the start and the end of Range. It is like Binary#subBinary() but note that Binary#subBinary() requires a length.

Code

var bin = <0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f>;
System.println(bin[2..12]);            // <0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c>
System.println(bin[2...12]);           // <0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b>
System.println(bin.subBinary(2, 10));  // <0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b>