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Postings from December 2013
Christian Walde wrote: >The i do not understand what "stereotyped use" means in simple >english. The variables are used in ways that tend to be the same between xsubs and are also peculiar to those particular variables. That they are used in the same peculiar ways does not happen merely because that's how we've always done it, which is what "tradition" implies. It happens because of the particular jobs they serve, which arises mainly from the problem space supplied by the Perl runtime's unique system of multiple stacks, which was partially described in Steffen's article. If you were to throw away all knowledge of XS and start from scratch, to write an xsub to operate in the Perl runtime, you would need the same concepts that XS already has. You would reinvent the variables. You wouldn't come up with the same names, of course. You wouldn't even necessarily name exactly the same things; for example, if your functions mostly have fixed arity, you likely wouldn't give the argument count a name. But for the most part you would find the same quantities are significant, and the exigencies of writing in C and attempting to be efficient would lead to you mostly putting the same ones into C variables. The only part that's really tradition is the specific names of the variables. As I said, you wouldn't naturally reinvent the same names if you were approaching the problem afresh. (A lot of people would come up with "items" and "sp", or at least names close to those, but "ax" is utterly arbitrary.) Outside the context of the code generated by XS, we use the same names for these variables just because they're the established names. -zeframThread Previous | Thread Next