Re: continuations (was Re: error() or nil, 'error msg')
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- Subject: Re: continuations (was Re: error() or nil, 'error msg')
- From: Coda Highland <chighland@...>
- Date: 2014年9月30日 13:02:37 -0700
On Tue, Sep 30, 2014 at 12:48 PM, Thiago L. <fakedme@gmail.com> wrote:
>
> On 30/09/14 04:37 PM, Coda Highland wrote:
>>
>> On Tue, Sep 30, 2014 at 12:21 PM, Tom N Harris <telliamed@whoopdedo.org>
>> wrote:
>>>
>>> On Wednesday, September 24, 2014 10:07:29 PM Andrew Starks wrote:
>>>>
>>>> Does this mean that we're going to loose coroutines? :)
>>>
>>> If by "loose" you mean "set free", then yes perhaps it will.
>>>
>>> (My apologies. It was too good to pass up.)
>>>
>>> But instead of seeing goto as a continuation, what if it's a tail-call?
>>>
>>> function A()
>>> local N=0
>>> local C=function()
>>> N=N+1
>>> goto B
>>> end
>>> N=1+C()
>>> ::B::
>>> return N
>>> end
>>> print(A())
>>>
>>> Does this print 1 or 2? Assuming a hypothetical Lua that allows such a
>>> thing.
>>>
>> It prints 1. You've skipped over the assignment instruction.
>>
>> /s/ Adam
>>
> If I got this right, the goto B is running A's code inside C... so it prints
> 2
>
No, the goto B is skipping over the normal control flow to continue
execution at the label. Think of it more like an exception than a
coroutine:
function A()
local N=0
local C=function()
N=N+1
error("goto B")
end
pcall(function() N=1+C() end)
-- ::B:: goes here
return N
end
print(A())
/s/ Adam
- References:
- error() or nil, 'error msg', Andrew Starks
- Re: continuations (was Re: error() or nil, 'error msg'), Roberto Ierusalimschy
- Re: continuations (was Re: error() or nil, 'error msg'), Andrew Starks
- Re: continuations (was Re: error() or nil, 'error msg'), Tom N Harris
- Re: continuations (was Re: error() or nil, 'error msg'), Coda Highland
- Re: continuations (was Re: error() or nil, 'error msg'), Thiago L.