Lazy evaluation in non-selected select cases

[Josh Bleecher Snyder]

One of the best things about learning Go has been that almost every time I ask "why doesn't it do <x> the way I expect?", the answer has been very instructive.

In that spirit, why aren't channel inputs in non-selected select cases evaluated lazily?

See:

http://play.golang.org/p/VIjggHHzT3

It seems to me that, in the second example, because nilChannel isn't selected in the case statement, there is no need to evaluate the proposed send value. The sample code is silly, but this would e.g. obviate the need for the variable first in http://talks.golang.org/2013/advconc.slide#30.

Cheers,

Josh

[Jesse McNelis]

On Wed, Jun 26, 2013 at 10:54 AM, Josh Bleecher Snyder <josh...@gmail.com> wrote:

One of the best things about learning Go has been that almost every time I ask "why doesn't it do <x> the way I expect?", the answer has been very instructive.

In that spirit, why aren't channel inputs in non-selected select cases evaluated lazily?

Once a choice is made the communication has begun and any time spent computing the channel input value is time spent blocking the channel.

It would be silly to block a channel while you did some large computation, it's far more reasonable to do the computation first.

See:

http://play.golang.org/p/VIjggHHzT3

It seems to me that, in the second example, because nilChannel isn't selected in the case statement, there is no need to evaluate the proposed send value. The sample code is silly, but this would e.g. obviate the need for the variable first in http://talks.golang.org/2013/advconc.slide#30.

Cheers,

Josh

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[Josh Bleecher Snyder]

>> One of the best things about learning Go has been that almost every time I ask "why doesn't it do <x> the way I expect?", the answer has been very instructive.
>>
>> In that spirit, why aren't channel inputs in non-selected select cases evaluated lazily?
>
>
> Once a choice is made the communication has begun and any time spent computing the channel input value is time spent blocking the channel.
> It would be silly to block a channel while you did some large computation, it's far more reasonable to do the computation first.

Thanks! That makes a lot of sense.

-josh