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
.
Alias of ENNReal.ofReal_lt_natCast
.
Alias of ENNReal.natCast_le_ofReal
.
Alias of ENNReal.ofReal_le_natCast
.
Alias of ENNReal.natCast_lt_ofReal
.
Alias of ENNReal.ofReal_eq_natCast
.
ENNReal.toNNReal
as a MonoidHom
.
Equations
- ENNReal.toNNRealHom = { toFun := ENNReal.toNNReal, map_one' := ENNReal.toNNRealHom.proof_1, map_mul' := ⋯ }
Instances For
Alias of ENNReal.iSup_natCast
.
Extension for the positivity
tactic: ENNReal.ofReal
.