Editing GNU Guile (section)

==Guile Scheme==
Guile Scheme is a [[General-purpose programming language|general-purpose]], [[high-level programming language]] whose flexibility allows expressing concepts in fewer [[lines of code]] than would be possible in languages such as [[C (programming language)|C]]. For example, its [[Macro (computer science)#Hygienic macros|hygienic macro system]] allows adding domain specific syntax-elements without modifying Guile. Guile implements the Scheme standard R5RS, most of R6RS and R7RS,<ref name=R7RS/> several [[Scheme Requests for Implementation]] (SRFI), and many extensions of its own.

The core idea of Guile Scheme is that "the developer implements critical algorithms and data structures in C or C++ and exports the functions and types for use by interpreted code. The application becomes a library of primitives orchestrated by the interpreter, combining the efficiency of compiled code with the flexibility of interpretation."<ref>Blandy 1997, p. 87.</ref>  Thus Guile Scheme (and other languages implemented by Guile) can be extended with new [[data type]]s and [[subroutine]]s implemented through the C API.

The standard distribution offers modules for Portable Operating System Interface ([[POSIX]]) system calls, [[Scheduling (computing)|scheduling]], a [[foreign function interface]], [[S-expression]] based [[XML]] processing through [[SXML]], SXPath, and SXSLT, [[HTTP]] and other [[World Wide Web]] APIs, [[delimited continuation]]s, [[array programming]],<ref name="Manual, Arrays" /> and other functionality.<ref name="Manual, API Reference" /><ref name="Manual, Guile Modules" />  Guile programs can use facilities from [[SLIB]], the portable Scheme library.<ref name="Manual, SLIB" />

===Implementation details===
When using [[continuation]]s with [[call/cc]], a requirement of the Scheme standard, Guile copies the execution [[Call stack|stack]] into the [[Dynamic memory allocation|heap]] and back.<ref name="Blandy quote call/cc" /> Its manual suggests using delimited continuations instead, because they have a more efficient implementation.<ref name="Guile Reference Manual Continuations Section" />

Because foreign code may have [[Pointer (computer programming)|pointer]]s to Scheme objects, Guile uses the conservative [[Boehm garbage collector|Boehm–Demers–Weiser]] (BDW) [[Garbage collection (computer science)|garbage collector]].<ref name="Guile Reference Manual Conservative GC Section" />