Editing Extensible programming (section)

=== Extensible compiler ===
In extensible programming, a compiler is not a monolithic program that converts source code input into binary executable output. The compiler itself must be extensible to the point that it is really a collection of plugins that assist with the translation of source language input into ''anything''. For example, an extensible compiler will support the generation of object code, code documentation, re-formatted source code, or any other desired output. The architecture of the compiler must permit its users to "get inside" the compilation process and provide alternative processing tasks at every reasonable step in the compilation process.

For just the task of translating source code into something that can be executed on a computer, an extensible compiler should:
* use a plug-in or component architecture for nearly every aspect of its function
* determine which language or language variant is being compiled and locate the appropriate plug-in to recognize and validate that language
* use formal language specifications to syntactically and structurally validate arbitrary source languages
* assist with the semantic validation of arbitrary source languages by invoking an appropriate validation plug-in
* allow users to select from different kinds of code generators so that the resulting executable can be targeted for different processors, operating systems, virtual machines, or other execution environment.
* provide facilities for error generation and extensions to it
* allow new kinds of nodes in the [[abstract syntax tree]] (AST),
* allow new values in nodes of the AST,
* allow new kinds of edges between nodes,
* support the transformation of the input AST, or portions thereof, by some external "pass"
* support the translation of the input AST, or portions thereof, into another form by some external "pass"
* assist with the flow of information between internal and external passes as they both transform and translate the AST into new ASTs or other representations