2011/2/11 Branko Čibej <br...@e-reka.si>: > On 11.02.2011 21:37, Daniel Becroft wrote: >> On Sat, Feb 12, 2011 at 6:07 AM, Grigory Petrov <grigory....@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
