Maps between real and extended non-negative real numbers #
This file focuses on the functions ENNReal.toReal : ℝ≥0∞ → ℝ
and ENNReal.ofReal : ℝ → ℝ≥0∞
which
were defined in Data.ENNReal.Basic
. It collects all the basic results of the interactions between
these functions and the algebraic and lattice operations, although a few may appear in earlier
files.
This file provides a positivity
extension for ENNReal.ofReal
.
Main theorems #
trichotomy (p : ℝ≥0∞) : p = 0 ∨ p = ∞ ∨ 0 < p.toReal
: often used forWithLp
andlp
dichotomy (p : ℝ≥0∞) [Fact (1 ≤ p)] : p = ∞ ∨ 1 ≤ p.toReal
: often used forWithLp
andlp
toNNReal_iInf
throughtoReal_sSup
: these declarations allow for easy conversions between indexed or set infima and suprema inℝ
,ℝ≥0
andℝ≥0∞
. This is especially useful becauseℝ≥0∞
is a complete lattice.
If a ≤ b + c
and a = ∞
whenever b = ∞
or c = ∞
, then
ENNReal.toReal a ≤ ENNReal.toReal b + ENNReal.toReal c
. This lemma is useful to transfer
triangle-like inequalities from ENNReal
s to Real
s.
If a ≤ b + c
, b ≠ ∞
, and c ≠ ∞
, then
ENNReal.toReal a ≤ ENNReal.toReal b + ENNReal.toReal c
. This lemma is useful to transfer
triangle-like inequalities from ENNReal
s to Real
s.
Alias of the reverse direction of ENNReal.ofReal_eq_zero
.
ENNReal.toNNReal
as a MonoidHom
.
Equations
- ENNReal.toNNRealHom = { toOneHom := { toFun := ENNReal.toNNReal, map_one' := ENNReal.toNNRealHom.proof_1 }, map_mul' := ⋯ }
Instances For
ENNReal.toReal
as a MonoidHom
.
Instances For
If x ≠ ∞
, then right multiplication by x
maps infimum over a nonempty type to infimum. See
also ENNReal.iInf_mul_of_ne
that assumes x ≠ 0
but does not require [Nonempty ι]
.
If x ≠ ∞
, then left multiplication by x
maps infimum over a nonempty type to infimum. See
also ENNReal.mul_iInf_of_ne
that assumes x ≠ 0
but does not require [Nonempty ι]
.
supr_mul
, mul_supr
and variants are in Topology.Instances.ENNReal
.
Extension for the positivity
tactic: ENNReal.ofReal
.