public static R FoldR <T, R>(Func <T, R, R> accumulator, R initVal, IEnumerable <T> list)
{
// 防止每次递归调用都创建 TailedSequence<T> 对象，做了优化处理
TailedSequence <T> _list = list as TailedSequence <T>;
_list = _list ?? new TailedSequence <T>(list);
if (list == TailedSequence <T> .Empty)
{
return(initVal);
}
return(accumulator(_list.Head, FoldR(accumulator, initVal, _list.Tail)));
}
public static R FoldL <T, R>(Func <R, T, R> accumulator, R initVal, IEnumerable <T> list)
{
// 防止每次递归调用都创建 TailedSequence<T> 对象做了，优化处理
TailedSequence <T> _list = list as TailedSequence <T>;
_list = _list ?? new TailedSequence <T>(list);
if (list == TailedSequence <T> .Empty)
{
return(initVal);
}
return(FoldL(accumulator, accumulator(initVal, _list.Head), _list.Tail));
}
