Hi,

I'm reading srfi-1 document from https://srfi.schemers.org/srfi-1/srfi-1.html#FoldUnfoldMap.

In "Fold, unfold & map" section, it says that

> This combinator presumably has some pretentious mathematical name;    interested readers are invited to communicate it to the author.

I am very curious about the mathematical name of this function because, before that, I've never heard of it.

For example,

Haskell provides `unfoldr` in its`Data.List` library. This `unfoldr` corresponds `unfold` in srfi-1, but Haskell does not provide a function, something called `unfoldl`, which corresponds to `unfold-right` in srfi-1.

My question is:

1. Is there any mathematical name behind `unfold-right` in srfi-1?
2. Can `unfold-right` be generalized to other data types, e.g. Tree? We know that `unfold` can be generalized to any recursive types (i.e. anamorphism).

Thanks.

Best regards,
Siyuan Chen