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Postings from January 2009
Author: Whiteknight Date: Mon Jan 5 12:54:48 2009 New Revision: 35007 Modified: trunk/docs/book/ch03_pir_basics.pod Log: [Book] Add some stubbish sections about classes and objects, that I'll expand on later. Modified: trunk/docs/book/ch03_pir_basics.pod ============================================================================== --- trunk/docs/book/ch03_pir_basics.pod (original) +++ trunk/docs/book/ch03_pir_basics.pod Mon Jan 5 12:54:48 2009 @@ -496,6 +496,34 @@ more familiar syntax for many of these control structures. We will discuss these libraries in more detail in A<CHP-6> "PIR Standard Library". +=head1 Classes and Objects + +It may seem more appropriate for a discussion of PIR's support for classes +and objects to reside in it's own chapter, instead of appearing in a generic +chapter about PIR programming "basics". However, part of PIR's core +functionality is it's support for object-oriented programming. PIR does't +use all the fancy syntax as other OO languages, and it doesn't even support +all the features that most modern OO languages have. What PIR does have is +support for some of the basic structures and abilities, the necessary subset +to construct richer and higher-level object systems. + +=head2 PMCs as Classes + +PMCs aren't exactly "classes" in the way that this term is normally used. +They are polymorphic data items that can be one of a large variety of +predefined types. As we have seen briefly, and as we will see in more depth +later, PMCs have a standard interface called the VTABLE interface. VTABLEs +are a standard list of functions that all PMCs implement N<or, PMCs can +choose not to implement each interface explicitly and instead let Parrot +call the default implementations>. + +VTABLES are very strict: There are a fixed number with fixed names and +fixed argument lists. You can't just create any random VTABLE interface that +you want to create, you can only make use of the ones that Parrot supplies +and expects. To circumvent this limitation, PMCs may have METHODS in +addition to VTABLES. METHODS are arbitrary code functions that can be +written in C, may have any name, and may implement any behavior. + =cut ##########################################################################