fix: dirac_isCountablyAdditive needs a sigma-algebra hypothesis - #643
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teorth merged 1 commit intoAug 11, 2026
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isCountablyAdditive carries B.isSigmaAlgebra as its first conjunct, so dirac_isCountablyAdditive as stated claimed every concrete Boolean algebra is a sigma-algebra — contradicted a section earlier by JordanMeasurable.boolean_algebra.not_isSigmaAlgebra. Take the sigma-algebra hypothesis instead; Example 1.4.29 is about measures on sigma-algebras. counting_isCountablyAdditive is fine as is, its algebra is the discrete one.
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isCountablyAdditivecarriesB.isSigmaAlgebraas its first conjunct, so Example 1.4.29 as stated claimed every concrete Boolean algebra is a σ-algebra — whichJordanMeasurable.boolean_algebra.not_isSigmaAlgebrarefutes a section earlier. added the hypothesis.counting_isCountablyAdditiveis fine as is since its algebra is ⊤.Generated by Claude Code