The Mysteries of Lisp (2015) | Hacker News Reader

The Mysteries of Lisp (2015)

arxiv.org

106 pointswslh20 comments

Disclaimer: if you read the following, mysteries will disappear O_o

- how to get started? https://lispcookbook.github.io/cl-cookbook/getting-started.h...

- is this mystery used in production©? quick look: https://lisp-journey.gitlab.io/who/

- is this mystery used by people for today's needs? https://github.com/CodyReichert/awesome-cl

This is a nice piece on "computer archeology". Given the academic nature of language design (I don't want to say "functional programing" or "LISP" here), it is obvious why it was written in the form of a scientific paper. If this was about the language C, I guess this would have been a blog post!

Note how ArXiV can be used for blogging: This paper is not peer reviewed but "only" uploaded to ArXiV. The site has some credibility barrieres which require invitation, but otherwise anybody can upload. I find this nice, but you should keep in mind this is just some academic variant of blogger.com ;-)

God damn I love Arxiv.

Ever since I started using miniflux, I have a stream of open papers that comes right to me. It's like being on the bleeding edge of human knowledge.

Is there an Arxiv RSS feed or something that you subscribe to?

https://arxiv.org/help/rss - Talks about the feeds and how to get to specific categories or subject areas within categories.

What is miniflux ? miniflux arxiv didn't return anything about a application,

https://miniflux.app/

It’s an rss reader.

My odd "entry" into this space, way before robotics (in a later second round of college), was via AutoLISP (the reduced use for AutoCAD). Lost touch with such for over 25+ years, but it was very fun at the time (a time when my other most used programming language was TurboPASCAL :-))

2015 in the title, 2018 in the linked .pdf file at https://arxiv.org/pdf/1505.07375.pdf

If you're going to be OCD about dates, please have them correct.

Not very interesting. Paip, lisp 1 game a time, even lisp in vim is more interesting. Or the paper about the beginning of lisp.

Has the author confused M-Expressions and F-Expressions or am I misreading this?

See footnote 6 on page 4:

> ‘F-expression’ [McCarthy 1959, p. 13] was the original name of M-expressions (for Meta- expressions) [McCarthy 1960, p. 187]. We choose the old name for two reasons: (1) meta is relative, the name M-expression becomes misleading once F-expressions are taken to the level of object language; (2) the term F-expression clearly indicates that functional [expressions] describe functions of S-expressions, which McCarthy called S-functions [1959, p. 1]. Nevertheless, in directly quoted text, we will keep the terms used in the source. [edited to remove hyphenated words]

F-expressions are functions taking unevaluated arguments, sort of a mixture of a macro and a function. It executes at runtime, whereas a macro executes at compile time(technically macro-expansion time). They were abandoned in mainstream LISP early on. However, John Shutt ironed out some of the issues with fexprs in his PhD thesis, which is a good read if you're interested in lisp internals[1]. He also designed a scheme like lisp dialect incorporating fexprs, called Kernel.

[1]: https://web.wpi.edu/Pubs/ETD/Available/etd-090110-124904/

The F-expressions in this paper are not the same thing as FEXPRs.

This was an internal, implementation terminology. Early Lisp has EXPR and SUBR routines: SUBR were written in machine language, and EXPR were interpreted functions. So EXPR doesn't mean "expression", but "function made of expressions that require code walking evaluation, rather than a straight machine-code subroutine ("SUBR") that can be called.

The F prefix denoted functions that implemented special forms. That may be where the F comes from: FEXPR and FSUBR. These F variants receive the unevaluated forms. So COND might be implemented as a FSUBR, which interprets it: walks the cond pairs, evaluates the test expressions, and so on. Whereas CAR and CDR would be SUBRS (no "F").

Kernel and it's successor wat (https://github.com/manuel/wat-js) has some great stuff, I personally prefer open composition from maru https://www.piumarta.com/freeco11/freeco11-piumarta-oecm.pdf as it combines fexprs and macros into one construct.

The author has confused himself for multiple people; one name appears on the paper which makes frequent references to some "we". Or possibly, it is the royal "we", as in "we are not amused". He's also confused himself for someone who is fit to give recommendations to Lisp implementors based on studying a thing or two about ancient history of syntax.

> If improper lists and circular lists are rarely used and can always be simulated in the rare case, it is better to kick them out to favor the common case.

"We" had better get a smidgeon of Lisp development experience, methinks. Plus, taking a look at Lisp from 1960 to 2022 wouldn't hurt, rather than obsessing about what MacCarthy meant when he said this and was he aware of that at that moment in 1959, and how should we do things today as a consequence. Good grief. Let's not have closures, because in 1959, MacCarthy saved and restored globals to simulate locals.

I thought it was pretty common to use 1st person plural in academic publications.

Yes, in a way that is inclusive of the reader. E.g "we next examine the implications of theorem 3". This guy uses it in ways that clearly refer only to himself, and not this rhetorical "we".

Is this something like a trailing comma in lists — a quirk to minimize diffs because you don't generally know when you start writing the paper whether you will remain the sole author or co-authors will join the work?

There's a footnote somewhere in there, I think to the effect that what later came to be called m-expressions were originally called f-expressions? Hence the weird terminology.

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