4118 better indexing for rewrite rules#4120
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… not fail rewrite)
…-sort-difference-with-functions
…g-for-rewrite-rules
`TopFun` index components are set to `Anything` before computing rule indexes to try. The effect is that all rules (for this index component) will be tried, leading to `Aborts` rather than getting `Stuck` (as the test with the unevaluated function shows).
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KEVM tests with insignificant slowdown
Likewise for kontrol tests:
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tothtamas28
approved these changes
Jul 17, 2025
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| syntax KItem ::= "Done" [symbol(Done)] | ||
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| syntax Abcd ::= "A" | "B" |
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Consider adding a new sort
syntax Ab ::= "A" [token]
| "B" [token]
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I tried that, but it actually breaks the demonstration of the unsound behaviour (because the tokens get index Anything and the Vrule gets tried first). So I just corrected the indexes in the comments and left the test as-is.
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I love the lattice formulation, that reflects unification properties very nicely! As long as we respect the properties of unification, we can be sure our rule indexing will be sound! |
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Indexing is extended to
Cell indexes form a (flat) lattice which is now explicit in a less-or-equal definition.
Rule selection now uses a function that selects all rule indexes which are (as a product lattice) greater than the inverted term index (i.e., top element becomes bottom element), with all function indexes turned into
Anything(top element) before the inversion. The new integration test shows why this is important for soundness.This addresses cases of unevaluated functions in indexed cells where previously booster would (likely) report
Stuckor (unlikely) a wrong result, while the result should beAborted(rules were excluded but they could apply depending on what kind of term the unevaluated function would return when evaluated).Fixes #4118