6daa55af82
This latest refactor adds "extractor macros" in place of the very-confusing-even-to-the-DSL-author reverse-rules-as-extractors concept. It was beautifully symmetric but also just too mind-bending to be practical. It also adds argument polarity to external extractors. This is inspired by Prolog's similar notion (see e.g. the "+x" vs. "-x" argument notation in library documentation) where the unification-based semantics allow for bidirectional flow through arguments. We don't want polymorphism or dynamism w.r.t. directions/polarities here; the polarities are static; but it is useful to be able to feed values *into* an extractor (aside from the one value being extracted). Semantically this still correlates to a term-rewriting/value-equivalence world since we can still translate all of this to a list of equality constraints. To make that work, this change also adds expressions into patterns, specifically only for extractor "input" args. This required quite a bit of internal refactoring but is only a small addition to the language semantics. I plan to build out the little instruction-selector sketch further but the one that is here (in `test3.isle`) is starting to get interesting already with the current DSL semantics.
9 lines
322 B
Plaintext
9 lines
322 B
Plaintext
- Optimizations
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- Infallible patterns; optimize away control flow when possible.
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- Don't do the closure-wrapping thing for expressions inside of patterns.
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- Document semantics carefully, especially wrt extractors.
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- Build out an initial set of bindings for Cranelift LowerCtx with extractors
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for instruction info.
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