Future cancellation

Bill Frantz frantz at pwpconsult.com
Wed May 1 11:04:01 PDT 2013

On 5/1/13 at 7:54 AM, jackalmage at gmail.com (Tab Atkins Jr.) wrote:

>On Wed, May 1, 2013 at 5:50 AM, Bill Frantz <frantz at pwpconsult.com> wrote:
>>On 4/30/13 at 11:04 PM, jackalmage at gmail.com (Tab Atkins Jr.) wrote:
>>> 1. Some promises are holding onto resources (locks, network
>>> connections, cpu time) which will be disposed of when they're
>>> finished.
>>I think this statement is wrong. Promises don't hold resources. They are a
>>placeholder for a value to be provided later. Perhaps the computation which
>>may provide the value at some future time holds a resource, or the
>>computation which will consume the value when it is resolved holds a
>>resource (generally a poor programming practice), but the promise itself
>>doesn't hold resources.
>Semantics.  ^_^  The promise can represent a computation, which can
>hold some releasable resources.

To my mind this is an important distinction. The promise does 
not represent the computation. It represents the result.

Any representation of the computation itself bring in a whole 
lot baggage which includes, the problem of managing distributed 
computation in the cloud plus a lot of other issues. Dragging 
this stuff into the base level of a programming language is a 
bad crossing of abstraction levels.

Cheers - Bill

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