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(author here) aye, this is a crucial point. any description language for binary formats quickly approaches turing complete, and i think this is what leads to so

(author here) aye, this is a crucial point. any description language for binary formats quickly approaches turing complete, and i think this is what leads to so many of the "transpile-first parser languages". i'm impressed how well kaitai has managed to wrangle that tendency towards turing-completeness; they do have an embedded expression language for attribute binding, and they do have 'repeat' and 'switch' constructs, but the language is astoundingly declarative. i think something very similar to kaitai could work if the tools to work with the files programmatically were ergonomic and available in many different languages. e.g., if the kaitai compiler were a native compiled library with lots of packaged FFI wrappers for many languages.

defanor 5y ago
Well, nothing stops Turing-complete languages from being declarative: lambda calculus is both, for instance, as well as some of the languages based on it (in particular parser combinators in Haskell and similar languages are neat and flexible). And there's indeed a practice of embedding some languages into others, though I think it ends up quite awkward to use, and in this case potential limitations (actually I don't know if kaitai is Turing-complete) may be undesirable. I imagine in many cases it may be simpler to ship, say, a parser/decoder (and/or printer/encoder) library providing a C API that is easy to call via FFI, rather than a description in a less common language, to be used with a particular library. But then again, probably that'd have its uses too.