Welcome to the conversation :)

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> If I have a list of ports `l` and want to read the contents of all of
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> them, `(map (cute read-string #f <>) l)` is one "obvious" way to go.
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> Another probably better example is #f, although not related to
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> generators & whatnot, which is commonly used as the "null value". Except
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> when it is a valid input or output value. And that's why `maybe` from
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> SRFI 189 is useful.
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> siiky

In another thread the Maybe approach was also mentioned.

The problem I have with eof-object in generator is that eof-object is not a disjoint type for a dijoint behavior such as described in null object pattern [0].
In a way that is similar to JavaScript's `undefined` that shows up in code or errors, without giving information about what is the actual context or problem.

[0] https://en.wikipedia.org/wiki/Null_object_pattern

FWIW, and AFAIU that is an idea that is strong in Kernel, but I can't quote precisely the R-1RK report at this time.

At least with the functional approach, the user is free to use whatever sentinel they decided is the best fit.