The binary minimum of real numbers is a short map

Content created by Fredrik Bakke and Louis Wasserman.

Created on 2026-01-01.
Last modified on 2026-01-01.

{-# OPTIONS --lossy-unification #-}

module real-numbers.short-map-binary-minimum-real-numbers where
Imports 
open import foundation.dependent-pair-types
open import foundation.universe-levels

open import metric-spaces.short-maps-metric-spaces

open import real-numbers.binary-maximum-real-numbers
open import real-numbers.binary-minimum-real-numbers
open import real-numbers.dedekind-real-numbers
open import real-numbers.isometry-negation-real-numbers
open import real-numbers.metric-space-of-real-numbers
open import real-numbers.negation-real-numbers
open import real-numbers.short-map-binary-maximum-real-numbers

Idea

For any a : ℝ, the binary minimum with a is a short map ℝ → ℝ for the standard real metric structure.

Proof

module _
  {l1 l2 : Level} (x : ℝ l1)
  where

  abstract opaque
    unfolding min-ℝ

    is-short-map-left-min-ℝ :
      is-short-map-Metric-Space
        ( metric-space-ℝ l2)
        ( metric-space-ℝ (l1 ⊔ l2))
        ( min-ℝ x)
    is-short-map-left-min-ℝ =
      is-short-map-comp-Metric-Space
        ( metric-space-ℝ l2)
        ( metric-space-ℝ (l1 ⊔ l2))
        ( metric-space-ℝ (l1 ⊔ l2))
        ( neg-ℝ)
        ( λ y → max-ℝ (neg-ℝ x) (neg-ℝ y))
        ( is-short-map-neg-ℝ)
        ( is-short-map-comp-Metric-Space
          ( metric-space-ℝ l2)
          ( metric-space-ℝ l2)
          ( metric-space-ℝ (l1 ⊔ l2))
          ( max-ℝ (neg-ℝ x))
          ( neg-ℝ)
          ( is-short-map-left-max-ℝ (neg-ℝ x))
          ( is-short-map-neg-ℝ))

  short-map-left-min-ℝ :
    short-map-Metric-Space
      ( metric-space-ℝ l2)
      ( metric-space-ℝ (l1 ⊔ l2))
  short-map-left-min-ℝ = (min-ℝ x , is-short-map-left-min-ℝ)

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