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Reword
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lowasser committed Feb 14, 2025
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19 changes: 12 additions & 7 deletions src/real-numbers/dedekind-real-numbers.lagda.md
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Expand Up @@ -54,13 +54,18 @@ A {{#concept "Dedekind real number" WD="real number" WDID=Q12916 Agda=ℝ}} `x`
consists of a [pair](foundation.dependent-pair-types.md) of _cuts_ `(L , U)` of
[rational numbers](elementary-number-theory.rational-numbers.md), a
[lower Dedekind cut](real-numbers.lower-dedekind-real-numbers.md) `L` and an
[upper Dedekind cut](real-numbers.upper-dedekind-real-numbers.md) `U`. A lower
Dedekind cut `L` is a subtype of the rational numbers that is
[inhabited](foundation.inhabited-subtypes.md) and rounded, meaning that `q ∈ L`
[if and only if](foundation.logical-equivalences.md) there exists `r`, with
`q < r` and `r ∈ L`. An upper Dedekind cut is a subtype of the rational numbers
that is inhabited and rounded "in the other direction": `q ∈ U` if and only if
there is a `p < q` where `p ∈ U`.
[upper Dedekind cut](real-numbers.upper-dedekind-real-numbers.md) `U`.

A lower Dedekind cut `L` is a subtype of the rational numbers that is

1. [Inhabited](foundation.inhabited-subtypes.md), meaning it has at least one
element.
2. Rounded, meaning that `q ∈ L`
[if and only if](foundation.logical-equivalences.md) there exists `r`, with
`q < r` and `r ∈ L`.

An upper Dedekind cut is analogous, but must be rounded "in the other
direction": `q ∈ U` if and only if there is a `p < q` where `p ∈ U`.

These cuts present lower and upper bounds on the Dedekind real number, and must
satisfy the conditions
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