intersperseWith<B> method

Iterable<B> intersperseWith<B>({ required Transformer<A, B> itemBuilder, required SeparatorBuilder<A, B> separatorBuilder, Transformer<A, B>? beforeFirst, Transformer<A, B>? afterLast, })

Creates a new Iterable with the separator interposed between elements.

Each element in the new iterable is built from the element in the original iterable using itemBuilder.

Each separator in the new iterable is built using separatorBuilder that accepts the original item before and after this separator.

If beforeFirst is not null and the iterable is not empty, beforeFirst is used as a separator builder that accepts the first element. The result of its call is prepended to the iterable.

If afterLast is not null and the iterable is not empty, afterLast is used as a separator builder that accepts the last element. The result of its call is appended to the iterable.

Implementation

Iterable<B> intersperseWith<B>({
  required Transformer<A, B> itemBuilder,
  required SeparatorBuilder<A, B> separatorBuilder,
  Transformer<A, B>? beforeFirst,
  Transformer<A, B>? afterLast,
}) sync* {
  final iterator = this.iterator;
  if (iterator.moveNext()) {
    if (beforeFirst != null) {
      yield beforeFirst(iterator.current);
    }

    yield itemBuilder(iterator.current);
    var prev = iterator.current;
    while (iterator.moveNext()) {
      yield separatorBuilder(prev, iterator.current);
      prev = iterator.current;
      yield itemBuilder(iterator.current);
    }

    if (afterLast != null) {
      yield afterLast(prev);
    }
  }
}