| Developer(s) | Free Software Foundation |
|---|---|
| Stable release | 2.0.3 (October 22, 2011[1]) [±] |
| Operating system | GNU |
| Type | Programming language |
| License | GNU Lesser General Public License |
| Website | http://www.gnu.org/software/guile/ |
| Standard(s) | R5RS |
GNU Guile is an interpreter/virtual machine for the Scheme programming language. It was first released in 1993.[2] Guile includes modularized extensions for POSIX system calls, APL array functionality, and others packaged as an object[3] library. "Libguile" allows the language to be embedded in other programs, and used as an interface for other languages which allow close integration.[4]
Guile stands for the GNU Ubiquitous Intelligent Language for Extensions, and is the official extension language of the GNU Project,[5] although, as of 2006, it has been used for only a handful of major projects. Its name was coined in a Usenet discussion by Lee Thomas.[6] The idea 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."[7]
Contents |
The close interaction between Guile and the application comes at a cost. Scheme requires implementations to optimize tail recursion because of Scheme's heavy use of recursion, but most techniques interfere with interoperation; Guile compromises by optimizing tail calls within purely Scheme functions and programs, but not when foreign functions enter the picture.[8] Implementation of call/cc, another requirement of the Scheme standard, is not entirely satisfactory — to handle continuations in this environment it must copy the entire execution stack into the heap, and back.[9] Because foreign code may have pointers to Scheme objects, Guile's garbage collector is the "conservative" variety which must periodically touch all of allocated memory.[10]
Guile had its origin in a heated discussion (later dubbed "the Tcl Wars") started by Richard Stallman, who stated that Tcl was underpowered for application scripting; he proposed Scheme as the preferred language for extending GNU applications and eventually launched the Guile project.[11] Because an appropriate Scheme interpreter did not exist at that time, Guile was developed to fill the niche. Tom Lord (later the developer of GNU arch) was heavily involved in the development of Guile while employed by Cygnus Solutions (later acquired by Red Hat). Its earlier versions were forked from SIOD ("Scheme In One Day"[12]) and the SCM interpreter,[13] before 1995.[14] After its initial release, development languished for many years, but 2009-10 saw major performance improvements.[15]
One of the goals of Guile is to allow other languages to be translated into Scheme and thence into portable byte-code; thus Guile would effectively be a language-neutral runtime environment. This goal has not been fulfilled yet, though various attempts have been made: a dialect of Scheme essentially differing only in its C-like syntax; a translation of Emacs Lisp; a Tcl converter motivated by tkWWW; and something roughly resembling the Logo programming language.[16]
Guile Scheme supports XML, XPath, and XSLT in the forms of SXML, SXPath and SXSLT, respectively. The S-expression-based XML processing is provided by guile-lib.
Guile programs can use facilities from SLIB, the portable Scheme library.
scm_cons, which is the underlying implementation of the Scheme procedures cons." Blandy 1997, pp. 94, 96.call/cc copies the entire C stack into the heap; invoking a continuation copies the stack back from the heap and uses the longjmp function to reactivate it. This implementation has a number of drawbacks…", Blandy 1997, p. 99.
|
|||||||||||||||||||