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.

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Alef was superseded by two programming environments.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

• 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: 1c1denINN441@darkstar.UCSC.EDU.