feat!: Decouple expression hashing and equality#277
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BREAKING: Expressions no longer use hashing for implementing equality BREAKING: Expression equality no longer takes commutativity into account In #276, @Shadow53 noted > One thing that may be useful enough to pull into its own PR is the > change to not use hashing in the implementation of `PartialEq` for > `Expression`, which also helps speed things up. We originally put this together in #27 to ensure that equality held in the face of commutativity, e.g., `1 + x == x + 1`. In addition to the performance benefits of decoupling the hashing and equality implementations, it makes sense to remove any special status for commutative operations in light of all the work we're doing on expression simplification. If we wished to ensure expressions are `Eq` if and only if they represent the same mathematical expression, we'd have to have equality contingent upon simplification, which would be even more costly.
kalzoo
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Aug 10, 2023
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Good to see it! |
Shadow53
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Aug 10, 2023
Shadow53
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Shadow53
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Looks good! Thanks for pulling this out of the other PR. Left a style nit, but it's fine to merge without.
| use Expression::*; | ||
| match self { | ||
| Address(m) => { | ||
| Expression::Address(m) => { |
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Small style nit, but while we're here: should use Self instead of Expression.
(It's fine not to make this change if there isn't anything more substantial being made. It's just a style thing that is triggered by a certain clippy lint)
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Thanks!
Yikes, I just ran cargo clippy -- -W clippy::pedantic 😮
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BREAKING: Expressions no longer use hashing for implementing equality
BREAKING: Expression hashing and equality no longer take commutativity into account
In #276, @Shadow53 noted
We originally put this together in #27 to ensure that equality held in the face of commutativity, e.g.,
1 + x == x + 1. In addition to the performance benefits of decoupling the hashing and equality implementations, it makes sense to remove any special status for commutative operations in light of all the work we're doing on expression simplification. If we wished to ensure expressions areEqif and only if they represent the same mathematical expression, we'd have to have equality contingent upon simplification, which would be even more costly.