Recursive `and_then`

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1

I'm looking for a recursive version of Option::and_then.

By that I mean that for an Option value, and_then(f) is called again and again recursively as long as the return value of f is Some(...), until stopping on None.

For a toy example:

let mut v = Vec::new();
Some(5).and_then_recurse(|n| match n {
    0 => None,
    _ => {
        v.push(n);
        Some(n - 1)
    }
});
assert_eq!(vec![5, 4, 3, 2, 1], v);

My implementation of this:

impl<T, F> AndThenRecurse<T, F> for Option<T>
where
    F: FnMut(T) -> Option<T>,
{
    fn and_then_recurse(self, mut f: F) -> Option<T> {
        match self {
            None => None,
            Some(t) => f(t).and_then_recurse(f)
        }
    }
}

My question would be:
Is there already something like this in the standard library, or some combination of functions that does this without requiring explicit recursion on my part?

2

You can do something similar with std::iter::successors:

let v: Vec<i32> = std::iter::successors(Some(5), |n| match n {
    1 => None,
    _ => Some(n - 1)
}).collect();
assert_eq!(v, vec![5,4,3,2,1]);
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3

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