HugoNikanors blogg‽

A blog about nothing, but mostly itself.

Lisps Quasiquotation

A while ago I noted that macros are the tool for handling code. I have since then realized just how powerful they are when left to their own devices. Previously I believed that quasiquotation would be hard to implement, having to seek the whole tree for unquotes, but the macro is simply

(define-syntax quasiquote
  (syntax-rules (unquote unquote-splicing)
    ((_ ,form)              form)
    ((_ (,@forms rest ...)) (append forms `(rest ...)))
    ((_ (lit     lits ...)) (cons   `lit  `(lits ...)))
    ((_ a)                  'a)))

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