I don't think you need to worry about the preprocessor for this (unless you want to use it.) And there are ways to do what you want to do dynamically during run time although if you use a compiler that doesn't have the library to do this for you (like MS .net) then it is a little difficult to implement. Jim Bromer
On Wed, Sep 11, 2013 at 10:22 PM, Russell Wallace <[email protected] > wrote: > C++ needs the most elaborate mechanism because of its legacy preprocessor: > http://en.wikipedia.org/wiki/Include_guard > > other languages like Java just refrain from having the compiler barf if > it's done twice, mostly. I don't know of any other languages that need an > elaborate mechanism, but I'm sure there are some; anyone here come across > one? > > > On Thu, Sep 12, 2013 at 3:17 AM, Piaget Modeler <[email protected] > > wrote: > >> Any pointers to those mechanisms? >> >> Cheers, >> >> ~PM >> >> ------------------------------ >> Date: Thu, 12 Sep 2013 03:12:13 +0100 >> Subject: Re: [agi] Module re-definitions >> From: [email protected] >> To: [email protected] >> >> >> If ( exists(table(A))) then drop table A ; >> >> Create table A as blah blah blah... >> >> >> ee? no! that would break everything that refers to table A. modify it in >> place instead. >> >> **** >> >> ** ** >> >> In 3 GL languages like C++, Java, etc. when a code module is accidentally >> >> included twice in a source file, what exactly happens? Does the compiler* >> *** >> >> redefine or ignore the functions or objects in the duplicate module? What >> **** >> >> about interpreted languages like python? >> >> >> what you want is usually that importing a module is idempotent, i.e. >> doing it twice is the same as doing it once. The mechanisms by which this >> is achieved are very different in C++ versus Java but it is achieved >> nonetheless. >> *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> >> <https://www.listbox.com/member/archive/rss/303/19999924-4a978ccc> | >> Modify <https://www.listbox.com/member/?&;> Your Subscription >> <http://www.listbox.com> >> *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> >> <https://www.listbox.com/member/archive/rss/303/1658954-f53d1a3f> | >> Modify <https://www.listbox.com/member/?&;> Your Subscription >> <http://www.listbox.com> >> > > *AGI* | Archives <https://www.listbox.com/member/archive/303/=now> > <https://www.listbox.com/member/archive/rss/303/24379807-f5817f28> | > Modify<https://www.listbox.com/member/?&;>Your Subscription > <http://www.listbox.com> > ------------------------------------------- AGI Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/21088071-f452e424 Modify Your Subscription: https://www.listbox.com/member/?member_id=21088071&id_secret=21088071-58d57657 Powered by Listbox: http://www.listbox.com
