to method

Iterable<int> to(int end, { int by = 1, })

Returns an iterable from this inclusive to end exclusive.

Example:

3.to(6); // (3, 4, 5)
2.to(-2); // (2, 1, 0, -1)

If by is provided, it will be used as step size for iteration. by is always positive, even if the direction of iteration is decreasing.

Example:

8.to(3, by: 2); // (8, 6, 4)

Implementation

Iterable<int> to(int end, {int by = 1}) {
  if (by < 1) {
    throw ArgumentError(
        'Invalid step size: $by. Step size must be greater than 0');
  }
  final count = ((end - this).abs() / by).ceil();
  // Explicit type declaration required for function argument.
  final int Function(int) generator = this >= end
      ? (index) => this - (by * index)
      : (index) => this + (by * index);
  return Iterable<int>.generate(count, generator);
}