feat!: Decouple expression hashing and equality #277
Merged
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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 areEq
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.