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You can acheive some composability (e.g. easily awaiting multiple events) by having first-class values for the coroutines/green-threads themselves. This is what

You can acheive some composability (e.g. easily awaiting multiple events) by having first-class values for the coroutines/green-threads themselves. This is what greenlet/gevent does, and it's rather pleasant to use. Try doing something like gevent.joinall() on Go though. https://nathanleclaire.com/blog/2014/02/15/how-to-wait-for-all-goroutines-to-finish-executing-before-continuing/ https://nathanleclaire.com/blog/2014/02/15/how-to-wait-for-a... Not fun. The other problem is that even with gevent, what you get is a first-class _coroutine_, not a first class class _continuation_. You have to actually spawn new coroutines (creating new stacks and going through sometimes unnecessary scheduler hoops) to get a first-class coroutine out of a possibly blocking function. Again, I'm not saying you can't do something like gevent.joinall(gevent.spawn(foo()), gevent.spawn(bar()), but: 1. Many languages don't support this (including Go and Lua, AFAIK). 2. It comes with its own tradeoffs again.

anonymoushn 10y ago
> 1. Many languages don't support this (including Go and Lua, AFAIK). I don't think this is necessarily a property of the primitives. greenlet doesn't support anything like gevent.joinall(gevent.spawn(foo()), gevent.spawn(bar()), but gevent does by adding python code to greenlet. So I'm sure that in the same manner one could do it in Lua using Lua's coroutines. (There might be some concern that we have the wrong primitive: greenlet provides symmetric coroutines and Lua provides asymmetric coroutines. I don't think it matters for this which one we use, but if it does it is simple to implement either in terms of the other.) That's not to say that the situation is ideal! To a great extent it's good if a language comes with a standard way to do this stuff! But it would be silly to say something like "Lua doesn't have inheritance" because it has a DIY inheritance construction kit instead of an "extends" keyword.

anonymoushn 10y ago

> 1. Many languages don't support this (including Go and Lua, AFAIK). I don't think this is necessarily a property of the primitives. greenlet doesn't support anything like gevent.joinall(gevent.spawn(foo()), gevent.spawn(bar()), but gevent does by adding python code to greenlet. So I'm sure that in the same manner one could do it in Lua using Lua's coroutines. (There might be some concern that we have the wrong primitive: greenlet provides symmetric coroutines and Lua provides asymmetric coroutines. I don't think it matters for this which one we use, but if it does it is simple to implement either in terms of the other.) That's not to say that the situation is ideal! To a great extent it's good if a language comes with a standard way to do this stuff! But it would be silly to say something like "Lua doesn't have inheritance" because it has a DIY inheritance construction kit instead of an "extends" keyword.