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+# Meta programming
+
+TODO: more (blog)
+
+Bruijn has a homoiconic meta encoding similar to Lisp's quoting feature.
+
+Blog post with more details: [Homoiconic self interpretation of lambda
+calculus](https://text.marvinborner.de/2023-09-03-21.html).
+
+## Encoding
+
+``` bruijn
+`X     ⤳ [[[2 (+Xu)]]]
+`(M N) ⤳ [[[1 `M `N]]]
+`[M]   ⤳ [[[0 `M]]]
+```
+
+Any quoted term gets converted to this encoding:
+
+``` bruijn
+# example quotations
+:test (`0) ([[[2 (+0u)]]])
+:test (`[0]) ([[[0 [[[2 (+0u)]]]]]])
+:test (`'0') ([[[0 [[[0 [[[0 [[[1 [[[2 (+0u)]]] [[[1 [[[2 (+0u)]]] [[[1 [[[2 (+0u)]]] [[[1 [[[2 (+0u)]]] [[[1 [[[2 (+1u)]]] [[[1 [[[2 (+1u)]]] [[[1 [[[2 (+0u)]]] [[[1 [[[2 (+0u)]]] [[[2 (+2u)]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]])
+
+# quotes are nestable!
+:test (``0) ([[[0 [[[0 [[[0 [[[1 [[[2 (+2u)]]] [[[0 [[[0 [[[2 (+0u)]]]]]]]]]]]]]]]]]]]]])
+:test (`[0 `0]) ([[[0 [[[1 [[[2 (+0u)]]] [[[0 [[[0 [[[0 [[[1 [[[2 (+2u)]]] [[[0 [[[0 [[[2 (+0u)]]]]]]]]]]]]]]]]]]]]]]]]]]])
+```
+
+## Quasiquotation
+
+Quoted terms can be escaped (*unquoted*) using the comma symbol.
+Unquoted terms will be fully evaluated first before getting quoted
+again.
+
+``` bruijn
+:test (```,[0]) (``[0])
+:test (`,`,[0]) ([0])
+:test (`[0 `,[0]]) (`[0 [0]])
+```
+
+Unquoted De Bruijn indices will get bound to the respective abstraction
+outside of its meta encoding.
+
+``` bruijn
+# adds two using normal quotation
+add-two `[0 + (+2u)]
+
+:test (!add-two (+2u)) ((+4u))
+
+# adds two using a reaching De Bruijn index
+add-two* [`(,0 + (+2u))]
+
+:test (!(add-two* (+2u))) ((+4u))
+```
+
+## Meta library [`std/Meta`](/std/Meta.bruijn.html)
+
+The meta library enables simple interaction with the meta encoding.
+
+Examples:
+
+``` bruijn
+# testing equivalence
+:test (α-eq? `[0 0] `[0 0]) (true)
+:test (α-eq? `α-eq? `α-eq?) (true)
+
+# BLC length of meta term
+:test (length `[0]) ((+4u))
+:test (length `[[1 1]]) ((+12u))
+```