range_util 0.0.4

A simple range iterator

Range Utils (for Dart)

Range Utils provides the common use case for generating an iteratble of numbers in sequential order.

There are a few ways to use Range Utils.

A NOTE ABOUT THESE EXAMPLES

In the examples below, I use .toList() and .take(...) to force the Range iterable to force computation and actually print something interesting. In practice you should almost never use these functions while using anything from range utils. Always just use the result of any range function or constructor without converting it to a list.

Using the Range constructor

The most basic functionality comes from using the default Range constructor.

It takes as parameters a start and an end point, and optionally an increment and an inclusive modifier.

> new Range(5, 10).toList(); [5 to 10] exclusive
[5,6,7,8,9]

> new Range(-5, 5, 2, true).toList(); [-5 to 5] by 2 inclusive
[-5, -3, -1, 1, 3, 5]

> new Range(10, 5, -2).toList(); // [10 to 2] by -2 exclusive
[10,8,6]

> new Range(0, 10, 2, true).toList(); // [0 to 10] inclusive
[0,2,4,6,8,10];

Using the Range.infinite constructor

Creating infinite ranges can also be handy. The Range.infinite constructor does this for you.

It takes as optional parameters start and increment numbers.

> new Range.infinite().take(10).toList();
[0,1,2,3,4,5,6,7,8,9]

> new Range.infinite(5).take(10).toList();
[5,6,7,8,9,10,11,12,13,14]

> new Range.infinite(5, 2).take(5).toList();
[5,7,9,11,13]

Providing a negative step will make it trend towards negative infinity.

> new Range.infinite(0, -1).take(5).toList();
[0,-1,-2,-3,-4]

Using py_range()

Because the idea for Range Util came from python, py_range emulates the behavior of python's xrange() function.

> py_range(5).toList();
[0,1,2,3,4]

> py_range(5,10).toList();
[5,6,7,8,9]

>py_range(5, 20, 2).toList();
[5,7,9,11,13,15,17,19]

Using range()

The range(...) function is meant to be used with named optional parameters to make the purpose of the arguments more clear.

> range(end: 5).toList();
[0,1,2,3,4]

> range(start: 5, end: 10).toList();
[5,6,7,8,9]

> range(start: 5, end: 10, step: 2).toList();
[5,7,9]

> range(start: 10, end: 20, step: 2, inc: true).toList();
[10,12,14,16,18,20]