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femtolisp: A lightweight, robust, scheme-like Lisp implementation

114 points by tosh 12 hours ago | 14 comments

borodi 10 hours ago

Fun fact, Julia's parser and part of its compiler are implemented in femtolisp, and you can access it using a not so secret option in the Julia CLI.

eigenspace 10 hours ago

We are slowly moving on replacing this stuff with implementations written in pure julia.

Currently the femtolisp parser is only used during bootstrapping the core systems so that we can parse the pure-julia parser and then we switch over to the julia parser. The same process is now happening with the femtolisp implementation of the lowering pass.

tokai 9 hours ago

So Julia will no longer be a LISP? :'(

joshjob42 4 hours ago

My night and weekend project the last month or so has been creating and implementing a package that provides a pure s-exp syntax for Julia that lowers to Julia's AST directly, and lately been churning through (mostly Opus is doing the actual churning) all the problems of creating an automatic transpiler for Julia to this other syntax.

Not ready to share just yet but nearly at the point that there are no Julia-syntax fallbacks in the entire base/stdlib and a femtolisp parser for the sexp syntax is able to build a complete Julia sysimage from the transpiled files. Already verified that I can transpile the .jl source of the Julia package for the syntax into the syntax, then use that transpiler to transpile again and load into the running sexp repl, then use that transpiler on the source again and get byte identical code, and along the way am testing to ensure that the entire Julia test suite passes in the sysimage being built.

So, with any luck here soon I'll have a sexp syntax for Julia that builds from raw transpiled sexp-syntax source and uses sexp syntax natively in the repl but can transpile & load any Julia code. Fingers crossed.

I'm aware of --lisp but it's not very good imo lol.

eigenspace 9 hours ago

Having some components written in lisp was never the lispy part of julia. The thing that makes julia lispy is its semantics and features.

tokai 9 hours ago

I agree. Was trying a tongue in cheek comment about how the Julia/LISP discussion over the years often would have someone point to julia --lisp as an argument for Julia being a LISP dialect.

markkitti 9 hours ago

    $ julia --lisp
    ;  _
    ; |_ _ _ |_ _ |  . _ _
    ; | (-||||_(_)|__|_)|_)
    ;-------------------|-----    ------------------------------    -----------------------
    > (+ 1 2)
    3

embedding-shape 7 hours ago

Slightly unrelated, but you take what (hn item) you can get: What is the smallest lisp (semantically/language-wise) people know, that could be used for implementing itself? Theoretical or practical/"real" is less relevant, mostly just curious. So far, it seems Bel (by pg) might get the closest, but can't claim to be an expert, surely could be something smaller out there?

pmcgoron 6 hours ago

Would SectorLISP (https://justine.lol/sectorlisp2/) count? It can run the LISP 1.5 metacircular evaluator.

soegaard 5 hours ago

This is pretty small.

http://scheme.dk/blog/2006/12/self-evaluating-evaluator.html

aportnoy 6 hours ago

Is Bel a smaller LISP than what's described in The Roots of Lisp? [1]

[1] https://paulgraham.com/rootsoflisp.html

anthk 6 hours ago

Check Zenlisp and Kilo Lisp under http://t3x.org

Not the smallest, but a great example on how a Lisp can be reimplemented.

Also, http://www.t3x.org/lisp64k/index.html

naasking 6 hours ago

Boot sector lisp?

https://github.com/jart/sectorlisp

danlitt 8 hours ago

Interesting! This seems superficially related to GNU Mes[1], although I imagine femtolisp does not require its small source to be written in a "simple" dialect of C.

[1]: https://www.gnu.org/software/mes/