Limbo (programming language)
Programming language
From Wikipedia, the free encyclopedia
Limbo is a programming language for writing distributed systems and is the language used to write applications for the Inferno operating system. It was designed at Bell Labs by Sean Dorward, Phil Winterbottom, and Rob Pike.[1]
| Limbo | |
|---|---|
| Paradigm | Concurrent |
| Designed by | Sean Dorward, Phil Winterbottom, Rob Pike |
| Developer | Historic: Bell Labs, Vita Nuova Holdings Current: Terzarima Systems, Inferno64 Project |
| First appeared | 1995 |
| Typing discipline | Strong |
| OS | Inferno |
| License | GNU GPL v2, see NOTICE in limbo subfolder of the tarball |
| Website | web |
| Major implementations | |
| Dis virtual machine | |
| Influenced by | |
| C, Pascal, CSP, Alef, Newsqueak | |
| Influenced | |
| Stackless Python, Go, Rust | |
The Limbo compiler generates architecture-independent object code which is then interpreted by the Dis virtual machine or compiled just before runtime to improve performance. Therefore all Limbo applications are completely portable across all Inferno platforms.[2][3]
Limbo's approach to concurrency was inspired by Hoare's communicating sequential processes (CSP), as implemented and amended in Pike's earlier Newsqueak language and Winterbottom's Alef.[1]
Language features
Limbo[2] supports the following features:
- modular programming
- concurrent computing
- strong type checking at compile and run-time
- interprocess communication over typed channels
- automatic garbage collection
- simple abstract data types
Virtual machine
The Dis virtual machine that executes Limbo code is a CISC-like VM, with instructions for arithmetic, control flow, data motion, process creation, synchronizing and communicating between processes, loading modules of code, and support for higher-level data-types: strings, arrays, lists, and communication channels.[4] It uses a hybrid of reference counting and a real-time garbage-collector for cyclic data.[5]
Aspects of the design of Dis were inspired by the AT&T Hobbit microprocessor, as used in the prototype BeBox.[3] A possible production of the formal logical specification for the Dis Virtual machine[6] has been discussed by Charles Forsyth of Terzarima Systems.[7] This is possible due to the regular structure and size of the virtual Machine compared to similar virtual machines.[6]
The Inferno64[8] project has extended the Dis virtual machine to 64-bits for application development on 64-bit architectures and platforms. [9]
Examples
Limbo uses Ada-style definitions as in:
name := type value;
name0,name1 : type = value;
name2,name3 : type;
name2 = value;
Hello world
implement Command;
include "sys.m";
sys: Sys;
include "draw.m";
include "sh.m";
init(nil: ref Draw->Context, nil: list of string)
{
sys = load Sys Sys->PATH;
sys->print("Hello World!\n");
}
Books
The 3rd edition of the Inferno operating system and Limbo programming language are described in the textbook Inferno Programming with Limbo[10] ISBN 0-470-84352-7 (Chichester: John Wiley & Sons, 2003), by Phillip Stanley-Marbell.
Another textbook The Inferno Programming Book: An Introduction to Programming for the Inferno Distributed System[11] was started by Martin Atkins, Rob Pike, Howard Trickey and Charles Forsyth[12] but never released.
See also
- The Inferno operating system
- Alef, the predecessor of Limbo
- Plan 9 from Bell Labs, operating system
- Go, similar language from Google
- AT&T Hobbit, a processor architecture which inspired the Dis VM