2011/2/11 Branko Čibej <brane_at_e-reka.si>:
> On 11.02.2011 21:37, Daniel Becroft wrote:
>> On Sat, Feb 12, 2011 at 6:07 AM, Grigory Petrov <grigory.v.p_at_gmail.com>wrote:
>>
>>> Hello.
>>>
>>> I'm learning subversion API right now and examining it's source code and
>>> examples. It's a lot of things in subversion source code that is called a
>>> "baton". For example, svn_cmdline_create_auth_baton() create "auth baton",
>>> and callbacks takes callback function pointer and, again, batons. I never
>>> heard of a term "baton" related to the programming. That is the "baton"
>>> concept subversion source code refers to? Maybe i can read somewhere about
>>> "batons" used in programming? Or is it a well-known term of some origin?
>>>
>>> Best,
>>> Grigory.
>>>
>> I don't know about subversion, but I'm guessing the origin of the baton
>> concept came from the running race [1], where an item is passed from runner
>> to runner. Historically, this baton would have some information on (or in)
>> it, that needed to get to its destination quickly.
>>
>> Not to be confused with baton twirling, though. [2]. :-)
>>
>> [1] http://en.wikipedia.org/wiki/Baton_%28running%29
>> [2] http://en.wikipedia.org/wiki/Baton_twirling
>
> The name does, in fact, come from the conductor's baton. The programming
> paradigm is old as programming itself, what we call a "baton" in SVN
> sources is variously called "userdata", "state", "context", etc. in
> other APIs that make use of callbacks.
>
> Its function is to allow the user of an API to pass an opaque object
> that gets passed back through callbacks so that the caller does not have
> to maintain a seprate context-discovery mechanism.
Hence the name 'baton': it gets passed around *a lot*. :)
-Hyrum
Received on 2011-02-11 22:30:04 CET