lisp

29 Articles

A RISC-V LISP Compiler…Written In Lisp

October 14, 2024 by 15 Comments

Ah, Lisp, the archaic language that just keeps on giving. You either love or hate it, but you’ll never stop it. [David Johnson-Davies] is clearly in the love it camp and, to that end, has produced a fair number of tools wedging this language into all kinds of nooks and crannies. The particular nook in question is the RISC-V ISA, with their Lisp-to-RISC-V compiler. This project leads on from their RISC-V assembler by allowing a Lisp function to be compiled directly to assembly and then deployed as callable, provided you stick to the supported language subset, that is!

The fun thing is—you guessed it—it’s written in Lisp. In fact, both projects are pure Lisp and can be run on the uLisp core and deployed onto your microcontroller of choice. Because who wouldn’t want to compile Lisp on a Lisp machine? To add to the fun, [David] created a previous project targeting ARM, so you’ve got even fewer excuses for not being able to access this. If you’ve managed to get your paws on the new Raspberry Pi Pico-2, then you can take your pick and run Lisp on either core type and still compile to native.

The Lisp-Risc-V project can be found in this GitHub repo, with the other tools easy enough to locate.

We see a fair few Lisp projects on these pages. Here’s another bare metal Lisp implementation using AVR. And how many lines of code does it take to implement Lisp anyway? The answer is 42 200 lines of C, to be exact.

Get Your Lisp On With The Dune Shell

September 20, 2024 by 10 Comments

Lisp is one of those programming languages that seems to keep taunting us for not learning it properly. It is still used for teaching functional languages today. [Adam McDaniel] has an obvious fondness for this fifty-year-old language and has used it in several projects, including their own shell, Dune.

Dune is a shell designed for powerful scripting. Think of it as an unholy combination of bash and Lisp.

Dune is designed to be highly customisable, allowing you to create a super-optimised workstation for your admin and programming tasks. [Adam] describes the front end for Dune as having turned up the cosiness dial to eleven, and we can see that. A cosy home is personalised, and Dune lets you customise everything.

Dune is a useable functional programming environment with a reasonably complete standard library to back it up, which should simplify some of the more complicated sysadmin tasks. [Adam] says the language also supports a few metaprogramming concepts, such as a quote operator, operator overloading, and macro programming. It’s difficult to describe much more about what you can do with Dune, as it’s a general-purpose programming language wrapped in a shell. The possibilities are endless, and [Adam] is looking forward to seeing what you lot out there do with his project!

The shell can be personalised by editing the prelude file, which allows you to overload functions for the prompt text, the incomplete prompt text (so you can implement intelligent completion options), and a function that deals with the formatting of the command response text. [Adam] gives us his personal prelude file, which defines many helper functions displaying useful things such as the current weather, a calendar, and an ASCII art cat. You never know when that might come in handy. This file is written in Lisp, so we reckon that’s where many people will start as they come up the Lisp (re)learning curve before embarking on more involved automation. Dune was written in Rust, so you need that infrastructure to install it with Cargo.

As we said earlier, Lisp is not a new language. We found a hack for porting a Lisp interpreter to any old language and also running Lisp bare metal on a Lisp machine. Finally, [Al] takes a look at some alternative shells.

The ’80s Multi-Processor System That Never Was

June 20, 2024 by 25 Comments

Until the early 2000s, the computer processors available on the market were essentially all single-core chips. There were some niche layouts that used multiple processors on the same board for improved parallel operation, and it wasn’t until the POWER4 processor from IBM in 2001 and later things like the AMD Opteron and Intel Pentium D that we got multi-core processors. If things had gone just slightly differently with this experimental platform, though, we might have had multi-processor systems available for general use as early as the 80s instead of two decades later.

The team behind this chip were from the University of Califorina, Berkeley, a place known for such other innovations as RAID, BSD, SPICE, and some of the first RISC processors. This processor architecture would be based on RISC as well, and would be known as Symbolic Processing Using RISC. It was specially designed to integrate with the Lisp programming language but its major feature was a set of parallel processors with a common bus that allowed for parallel operations to be computed at a much greater speed than comparable systems at the time. The use of RISC also allowed a smaller group to develop something like this, and although more instructions need to be executed they can often be done faster than other architectures.

The linked article from [Babbage] goes into much more detail about the architecture of the system as well as some of the things about UC Berkeley that made projects like this possible in the first place. It’s a fantastic deep-dive into a piece of somewhat obscure computing history that, had it been more commercially viable, could have changed the course of computing. Berkeley RISC did go on to have major impacts in other areas of computing and was a significant influence on the SPARC system as well.

Forsp: A Forth & Lisp Hybrid Lambda Calculus Language

June 13, 2024 by 16 Comments

In the world of lambda calculus programming languages there are many ways to express the terms, which is why we ended up with such an amazing range of programming languages, even if most trace their roots back to ALGOL. Of the more unique (and practical) languages, Lisp and Forth probably range near the top, but what if you were to smudge both together? That’s what [xorvoid] did and it resulted in the gracefully titled Forsp programming language. Unsurprisingly it got a very warm and enthusiastic reception over at Hacker News.

While keeping much of Lisp-isms, the Forth part consists primarily out of it being very small and easy to implement, as demonstrated by the C-based reference implementation. It also features a Forth-like value/operand stack and function application. Also interesting is Forsp using call-by-push-value (CBPV), which is quite different from call-by-value (CBV) and call-by-name (CBN), which may give some advantages if you can wrap your mind around the concept.

Even if practicality is debatable, Forsp is another delightful addition to the list of interesting lambda calculus demonstrations which show that the field is anything but static or boring.

Die of an Altera EPM7032 EEPROM-based Complex Programmable Logic Device (CPLD). (Credit: ZeptoBars, Wikipedia)

Using EPROMS And EEPROMs As Programmable Logic With Lisp

October 28, 2023 by 9 Comments

That EPROMs, EEPROMs and kin can be used as programmable logic should probably not come as a major surprise, but [Jimmy] has created a Lisp-based project that makes using these chips as a logic array very straightforward. All it takes is importing the package into one’s Lisp project and defining the logic, before the truth function generates the binary file that can be written to the target chip.

Suggested is the one-time-programmable AT27C512R EPROM (64k x8), but any 8-bit parallel interface (E)EPROM should work, with non-OTP chips being nice unless the chip has to go into a production device. A possible future improvement is the addition of 16-bit (E)EPROM support.

The use of EEPROMs is common with PLA-replacements, as with, for example, the Commodore 64, where the official PLA IC tends to go bad over time. Due to the complexity of the logic in these PLA ICs, here CPLDs are used, which internally are still EEPROM-based, but feature many more programmable elements to allow for more complex logic. If all you need is a bit of glue logic and you are looking for something in between a stack of 74-logic ICs and a CPLD, an EEPROM may be just be the solution, regardless of whether you prefer to create the binary image with Lisp or C.

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When The Sojourner Mars Rover Nearly Ran LISP

August 7, 2023 by 12 Comments

During the late 1980s NASA’s Jet Propulsion Laboratory (JPL) was busy developing the first ever wheeled robot that would roam the surface of Mars. Due to the long round-trip times of any signals between Mars and Earth, development of the firmware that would control the rover was a major point, with the two teams occupied with the task each picking different levels of autonomy for the rover. In a retrospective, [Ron Garrett] who worked at JPL on the ‘more autonomy’ team describes his recollections.

Whereas [Ron]’s team focused on creating a rover that could be provided with high-level instructions which the sophisticated LISP-based firmware would use as guidelines to navigate and operate by, the other team pursued a more limited autonomy approach whereby a human driver would use explicitly plan out the route which the rover would follow before awaiting new instructions.

Perhaps unsurprisingly, the system requirements for running LISP and the additional uncertainties and complexities with the autonomous approach, as well as testing and validating the firmware, resulted in the Sojourner Mars rover featuring the latter approach, with straightforward C-based firmware. Most of Sojourner’s autonomy was limited to a home return function if communication with the lander was lost, which limited both its range and operations during its 85-day extended mission.

As [Ron] covers with examples from later missions, one advantage of LISP is that it allows you to send instructions which can be interpreted (e.g. to debug the system) without having to program in such functionality explicitly. With later Mars rover missions much more of this autonomy that [Ron]’s team pioneered was implemented, although C remained the language of choice for these later rovers.

Heading image: Ron Garrett standing in front of the Robbie prototype. Rocky III can be see in the lower left, and above him are Rajiv Desai and Robert Ivlev, two other members of the team. (Credit: Ron Garret)

Reviving Interlisp With The Medley Interlisp Project

July 9, 2023 by 21 Comments

Within the Artificial Intelligence and natural language research communities, Lisp has played a major role since 1960. Over the years since its introduction, various development environments have been created that sought to make using Lisp as easy and powerful as possible. One of these environments is Interlisp, which saw its first release in 1968, and its last official release in 1992. That release was Medley 2.0, which targeted various UNIX machines, DOS 4.0, and the Xerox 1186. Courtesy of the Interlisp open source project (GitHub), Medley Interlisp is available for all to use, even on modern systems.

The documentation contains information on how to install Medley on Linux but also Mac and Windows (via WSL1 or WSL2). For those just curious to give things a swing, there’s also an online version you can log into remotely. What Medley Interlisp gets you is an (X-based) GUI environment in which you can program in Lisp, essentially an IDE with a debugger and the (in)famous auto-correction tool for simple errors such as typos, known as the DWIM (Do What I Mean), which much like the derived version in Emacs seeks to automatically fix simple issues like misspellings without forcing the developer to fix it and restart the compilation.

Thanks to [Pixel_Outlaw] for the tip and for also telling us about a project they wrote using Medley Interlisp for the Spring Lisp Game Jame 2023 titled Interlisp Fifteen Puzzle.