Alef (programming language)

Alef is a discontinued concurrent programming language, designed as part of the Plan 9 operating system by Phil Winterbottom of Bell Labs. It implemented the channel-based concurrency model of Newsqueak in a compiled, C-like language.

Alef

Paradigm	compiled, concurrent, structured
Designed by	Phil Winterbottom
First appeared	1992
Typing discipline	Static, strong
OS	Plan 9 from Bell Labs
Influenced by
C, Newsqueak
Influenced
Limbo, Rust, Go

History

Alef appeared in the first and second editions of Plan 9, but was abandoned during development of the third edition.[1][2] Rob Pike later explained Alef's demise by pointing to its lack of automatic memory management, despite Pike's and other people's urging Winterbottom to add garbage collection to the language;[3] also, in a February 2000 slideshow, Pike noted: "…although Alef was a fruitful language, it proved too difficult to maintain a variant language across multiple architectures, so we took what we learned from it and built the thread library for C."[4]

Alef was superseded by two programming environments. The Limbo programming language can be considered a direct successor of Alef and is the most commonly used language in the Inferno operating system. The Alef concurrency model was replicated in the third edition of Plan 9 in the form of the libthread library, which makes some of Alef's functionality available to C programs and allowed existing Alef programs (such as Acme) to be translated.[5]

Example

This example was taken from the Alef reference manual.[1] The piece illustrates the use of tuple data type.

(int, byte*, byte) 
func() 
{ 
    return (10, "hello", ’c’); 
}

void 
main() 
{
    int a; 
    byte* str; 
    byte c; 
    (a, str, c) = func(); 
}

See also

• Communicating sequential processes
• Plan 9 from Bell Labs

References

1. Winterbottom, Phil (1995). "Alef Language Reference Manual". Plan 9 Programmer's Manual: Volume Two. Murray Hill: AT&T.
2. "Preface to the Third (2000) Edition". Plan 9 Manual. Murray Hill: Bell Labs. June 2000. Retrieved 2012-10-29.
3. Pike, Rob (2010). Origins of Go concurrency style. OSCON Emerging Languages Camp.
4. Pike, Rob. "Rio: Design of a Concurrent Window System" (PDF). Retrieved 8 March 2013.
5. "thread(2)". Plan 9 Manual. Retrieved 2012-10-29.

• Flandrena, Bob (1995). "Alef Users' Guide". Plan 9 Programmer's Manual: Volume Two. Murray Hill: Bell Labs.
• Phil Winterbottom (1992-10-20). "Plan9 VM". Newsgroup: comp.os.research. Usenet: [email protected].