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README.md

Sild

Sild Is a Lisp Dialect! Sild also means "herring" in Danish. It's also an anagram of "lisp" if you flip the 'p' around.

.        `\\\,
|\ _.--''""````"''--._
  }sild             o `\
|/ '--.._____'`'_._..~~`
`

Why did you do this?

For the learns. I wrote three iterations of this language. The first one was a disaster! The second I got working pretty well! But then I tried to explain it to someone and completely couldn't, so I threw it all out and started over for a 3rd time, making really atomic commits and writing blog posts about the whole thing as I was developing it. Those posts currently live here:

blog.jfo.click

Sild could best be described as a busted scheme-like lisp. I did not attempt to achieve compliance with any existing standard, but in the absence of a compelling reason to the contrary I would default to a scheme-like design. I used Petite Chez Scheme as a model in these instances.

I learned an enormous amount from this project, about Lisp history and practice, about C, and about language design in general. Sild still has a long way to go before it could be considered useful, but it is nonetheless, in a very real sense, already a functioning programming language.

Installation

git clone http://github.com/urthbound/sild
cd sild

and then...

make

That should work on OSX! It will probably work on other systems, too, but I don't know that for sure.

That will give you a sild executable that you can execute directly, or put on your path.

Usage:

$ ./sild filename.sld

... in the directory where sild lives Will run the file specified by filename.sld! I've chosen .sld as the Sild extension. Because it is 3/4 of the same letters. Very clever.

Syntax

Sild is a lisp dialect. Right now, it supports the following:

quote
car
cdr
cons
eq
atom
cond

(And also the ' macro!)

It has two top level only void return value functions!

define
display

And it has lambdas!

lambda

For more detailed explanations and examples, see examples/basics.sld

You can top level bind whatever to these canonical names, I enjoy this one:

(define λ lambda)

You could in theory do this for all the keywords! Here is a fully functional Japanese example.

Todo

Oh so, so much! For starters, there's an enormous memory leak with regard to persistent procedure environments. So I need proper garbage collection of some kind!

It would be nice to have more effective error messages in general, and a stack trace!

And a proper cross platform makefile!

Also there are no numbers or mathematical operations, or strings or string operations, or types of any kind really, or system IO.

And it's not properly tail call optimized! This is a big one.

And there is no repl, either! A lisp without a repl, for shame, for shame.

I consider these features to be beyond the working v0.1 prototype presented here, and look forward to studying how to implement them in the future! I wanted very much to do all these things and then release the whole language at once, but I would never have finished, frankly, and the original intent was to implement a minimal lisp in which I would be able to write non-trivial lambda calculus in. It can do that now, so hooray!

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