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Comment by vnorilo | Hacker News Reader

Homoiconicity is the googlable term. The first Lisp book that blew my mind is SICP, nowadays free: https://sicp.me/sicp.pdf I think you need a big picture to appreciate the depth of homoiconicism and meta-circularity. It's a big one, but well worth it IMO.

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I remember finding it pretty revelatory the first time I saw LET defined as a macro like

    (defmacro let (bindings &body body)
      `((lambda ,(mapcar #'first bindings) ,@body)
        ,@(mapcar #'second bindings)))

Seeing it use MAPCAR like that just made something click for me for whatever reason.

To add on, Racket in particular has some very slick syntax for writing these kinds of things:

  (define-syntax-rule
    (let ([id expr] ...) body ...)
    ((λ (id ...) body ...) expr ...))

I definitely liked this about Racket but I did also find the elipses to be a bit magic to begin with...

As with all things, the trick to chase the magic away is to implement them. I recently made a little term rewriting library using racket/match syntax but with the pattern/templates specifiable at runtime. Ellipses were a bit confusing to begin with but when you break list patterns down into cons pairs + a cons-like pattern binary combinator to represent ellipses, it started making sense. The unexpected thing for me was that I thought nested ellipses were going to be the tough part, but it turns out they actually just... work.

Stuart Sierra has an interesting talk on homoiconicity and its history: https://www.youtube.com/watch?v=o7zyGMcav3c

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