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| author | Taylan Kammer <taylan.kammer@gmail.com> | 2026-06-20 22:53:50 +0200 |
|---|---|---|
| committer | Taylan Kammer <taylan.kammer@gmail.com> | 2026-06-20 22:53:50 +0200 |
| commit | b84ed4f563b3536365f7d3cc4d068407e98685b3 (patch) | |
| tree | 9ab7b18d712db1329b6230cb45520e7c85dc46fd /doc/0/2-decode.md | |
| parent | bfaa74b19fc81dbe071d55566a78a8e329237eff (diff) | |
Diffstat (limited to 'doc/0/2-decode.md')
| -rw-r--r-- | doc/0/2-decode.md | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/doc/0/2-decode.md b/doc/0/2-decode.md new file mode 100644 index 0000000..1a45824 --- /dev/null +++ b/doc/0/2-decode.md @@ -0,0 +1,44 @@ +# Decoding + +A separate process called "decoding" can transform simple data structures, +consisting of only the base datum types, into a richer set of Zisp types. + +For example, the decoder may turn `(#HASH ...)` into a vector, as one would +expect a vector literal like `#(...)` to work in Scheme. Bytevector syntax +could use a custom rune as a list prefix, like: `#u8(...)` + +Runes may be decoded in isolation as well, rather than transforming a list +whose head they appear in. This can implement Boolean constants as `#true` +and `#false` or `#t` and `#f`. + +The decoder recognizes `(#QUOTE ...)` to aid in implementing the traditional +quoting mechanism of Lisp/Scheme, but with a significant difference: + +Traditional quote is "unhygienic" in Scheme terms. An expression such as +`'(foo bar)` will always be read as `(quote (foo bar))` regardless of what +lexical context it appears in, so the semantics will depend on whatever the +identifier `quote` is bound to, meaning that the expression may end up +evaluating to something other than the list `(foo bar)`. + +The Zisp decoder, which transforms not datum to datum, but object to object, +can turn `#QUOTE` into an object which encapsulates the notion of quoting, +which the Zisp evaluator can recognize and act upon, ensuring that an +expression like `'(foo bar)` always turns into the list `(foo bar)`. + +One way to think about this, in Scheme (R6RS / syntax-case) terms, is that +expressions like `'(foo bar)` turn directly into a syntax object when read, +and the created syntax object begins with an identifier bound to `quote` in +the standard library. + +The decoder is, of course, configurable and extensible. The transformations +mentioned above would be performed only when it's told to decode data which +represents Zisp code. The decoder may be given a different configuration, +telling it to decode, for example, data which represents a different kind of +domain-specific data, such as application settings, build system commands, +complex data records with non-standard data types, and so on. + +<!-- +;; Local Variables: +;; fill-column: 80 +;; End: +--> |
