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Dedekind finiteness of various notions of finite type #1422

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Dedekind finiteness of various notions of finite type #1422

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@fredrik-bakke fredrik-bakke commented May 2, 2025 •
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Defines

  • Subfinite types
  • Subfinitely indexed types
  • Dedekind finite types
  • dual Dedekind finite types
  • Noninjective maps (maps for which there exists a repetition of values)

Proves

  • Subfinite types are Dedekind finite
  • Subfinitely indexed types are Dedekind finite
  • Dedekind finite types validate the Cantor–Schröder–Bernstein theorem constructively
  • finite choice under the double negation modality
  • factor property of connected maps

+lost of small refactoring work

Resolves #748

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Define the predicate that f maps two different elements to the same value
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