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LeanPool.NFWeakPartition.NFStandard.HailperinUnitUnion

NF weak partition development: NFStandard.HailperinUnitUnion.

typeLower turns a relation-like object R into the set of z for which every pair ⟨w,{z}⟩ belongs to R. Taking R = V × (V \ A) and then a complement therefore removes exactly one singleton level from the membership test.

Remove one singleton level from the elements tested against A.

Equations
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Instances For
    @[simp]

    Exact semantic law for one level of singleton lowering.

    @[simp]

    Iterated lowering is inverse, at the membership level, to raise.