TITLE 
internals - Design and Implementation of Pipp
Source code
See pipp.pod on where to get the code.
Issue tracking
Not decided yet. Will be documented in pipp.pod. See also ../ROADMAP.
Testing
See testing.pod.
Parsing
Parsing is done with Parrot Compiler Toolkit, PCT.
Bytecode generation
The parse tree is transformed to a Parrot Abstrace Syntax Tree. PIR und Bytecode is then generated from the PAST.
Variables
List of scopes and types of variables.
- globals in top file Lexical. Might need extra treatment.
- globals in included files Lexical in scope of the included file.
- Class constants Class constants are stored a package variables in the namespace $?NS ~ '\\' ~ $?CLASS ~ '::'. The trailing '::' guarantees that there is no conflict with namespace constants.TODO: make them readonly
- Static class members Like class constants, but writable.
- Class members
- function and method scope Lexical is scope of the function or method.
- $this Bound to register
- constants Currently constants are stored in the hash ['pipp'; 'php_constants']. The functions
self.
define and defined access this package scoped hash.
This approach works good enough for constants in the global namespace.
For namespaced constants the above approach could be extended to consider the namespace part of the constant,
the current namespace and the active namespace aliases.Another approach is to treat constants as namespaced variables and work with standard PAST techniques.
Experiments using that approach are underway.Functions and closures
TODO: type hints in function declarations
Builtin functions
Closures
There is a major bug in the implementation.
TODO: see t/php/closures.t
Internal functions
Object orientation
Namespaces
A namespace is introduced with the keyword namespace. The namespaced code can be enclosed in brackets. The namespace declaration needs to be the first statement in the file. With brackets, there can be multiple namespaces per file. Nesting is not possible. Namespaces don't carry over to included files. define() doesn't define in the current namespace. The backslash character serves as the namespace separator. Short names can be defined with use. Only classes, functions and constants are namespaced. The current namespace can be queried with __NAMESPACE__. Namespaces are case insensitive. No global code can precede the first namespace directive.
Implementation in Pipp
In order to ease implementation and testing, there are some divergences in Pipp.
- Only the bracketed syntax is supported.
- Code outside the scope of namespaces directives is allowed.
- 'const' outside a declared namespace is allowed.
SEE ALSO
- http://docs.php.net/manual/en/language.namespaces.php
- http://docs.php.net/manual/en/language.namespaces.faq.php
- http://wiki.php.net/rfc/namespaces
- http://wiki.php.net/rfc/namespaceseparator
- http://wiki.php.net/rfc/backslashnamespaces
- http://wiki.php.net/rfc/namespacecurlies
- http://wiki.php.net/rfc/namespaceref
- http://inside.webfactory.de/en/blog/php-namespaces-explained.html
- http://marc.info/?l=php-internals&m=121527668606247
- http://bugs.php.net/bug.php?id=46304
- http://loveandtheft.org/2008/10/26/set-sail-for-fail-php-namespaces/
Including and requiring
require_once() is supported,
but might have issues with variables.
Extensions
Implementation in Pipp
Currently, Pipp has no support at all for extensions.
SEE ALSO
TODO: Embedding and Extending PHP, by Sahrah ... L<http://www.php.net/manual/en/internals2.php>
Interaction with the Parrot world
Using Modules from other HLLs. Inlining PIR and other languages.
Compatability
See pipp.pod for a list of divergences.
Related projects.
See the Wiki. Roadsend, Zend, PHC.
AUTHOR
Bernhard Schmalhofer - <Bernhard.Schmalhofer@gmx.de>
