From: Knut.Franke@...
Date: 2014-10-18T13:55:51+00:00
Subject: [ruby-core:65782] [ruby-trunk - Feature #10344] [PATCH] Implement	Fiber#raise

Issue #10344 has been updated by Knut Franke.

File 0001-Implement-Fiber-raise.patch added
File 0001-Implement-Fiber-raise-in-ext-fiber.patch added

> I understand this feature helps some libraries. But I can't understand why it is important.

Without Fiber#raise, libraries need to use some rather inelegant and inefficient workarounds (wrapping or tagging exceptions, wrapping Fiber.yield etc). Also, having Thread#raise arguably leads one to expect the same functionality in Fiber. I'm not sure whether the feature qualifies as "important", but I still think it is worth including.

> Basically, I want to recommend strongly that using Fiber as semi-croutine, ristricted feature.

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.

> At least, such feature should be located at ext/fiber.

I disagree, because the feature is applicable to the restricted (semi-coroutine) fibers available without requiring 'fiber', and indeed implementable on top of them. Nevertheless, I've attached a variant of the patch which adds the method only in ext/fiber (as a compromise solution).

----------------------------------------
Feature #10344: [PATCH] Implement Fiber#raise
https://bugs.ruby-lang.org/issues/10344#change-49518

* Author: Knut Franke
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
----------------------------------------
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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