Issue #10344 has been updated by Knut Franke.


Koichi Sasada wrote:
> > I think [Consumer](http://nome.github.io/coroutines/Consumer.html) is an example of a semi-coroutine (in the sense that it uses Fiber.yield, not Fiber#transfer) that benefits from having Fiber#raise.
> 
> Interesting. I don't know details of this library. Could you explain why it is important in this library?

Consumer provides an abstraction for (semi-)coroutines that accept (consume) values; analogous to an Enumerator, which produces (enumerates) values. Since a consumer may need to do resource cleanup and/or produce a final result, we need some way to signal end of values. I think the most natural way to do this is to raise StopIteration in the consumer: The situation is analogous to calling Enumerator#next when no more values are available, and StopIteration terminates Kernel#loop, which often allows writing consumers very concisely.

In general, I think Fiber is a powerful primitive that can be used by libraries to build abstractions like Enumerator, Consumer and others. While Enumerator does not require the #raise feature, other abstractions can very well benefit from it.

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Feature #10344: [PATCH] Implement Fiber#raise
https://bugs.ruby-lang.org/issues/10344#change-49634

* Author: Knut Franke
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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While it is possible to implement this in pure Ruby (by wrapping Fiber.yield and Fiber#resume), this feels like a low-level feature that ought to be provided out of the box. Also, the C implementation is more straight-forward, and more efficient. Unfortunately, it is not quite possible to implement this as a C extension module (without resorting to wrappers again); cf. the change to make_passing_arg().

Example usage:

~~~
fib = Fiber.new do
  counter = 0
  loop { counter += Fiber.yield }
  counter
end
fib.resume
fib.resume 10
fib.resume 100
fib.raise StopIteration # => 110
~~~

---Files--------------------------------
0001-Implement-Fiber-raise.patch (4.12 KB)
0001-Implement-Fiber-raise.patch (3.51 KB)
0001-Implement-Fiber-raise-in-ext-fiber.patch (3.6 KB)


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