Power function on ℝ≥0 and ℝ≥0∞ #
We construct the power functions x ^ y where
xis a nonnegative real number andyis a real number;xis a number from[0, +∞](a.k.a.ℝ≥0∞) andyis a real number.
We also prove basic properties of these functions.
The nonnegative real power function x^y, defined for x : ℝ≥0 and y : ℝ as the
restriction of the real power function. For x > 0, it is equal to exp (y log x). For x = 0,
one sets 0 ^ 0 = 1 and 0 ^ y = 0 for y ≠ 0.
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Variant of NNReal.rpow_add' that avoids having to prove y + z = w twice.
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rpow version of Multiset.prod_map_pow for ℝ≥0.
rpow version of Finset.prod_pow for ℝ≥0.
rpow version of Multiset.prod_map_pow.
rpow version of Finset.prod_pow.
Bundles fun x : ℝ≥0 => x ^ y into an order isomorphism when y : ℝ is positive,
where the inverse is fun x : ℝ≥0 => x ^ (1 / y).
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The real power function x^y on extended nonnegative reals, defined for x : ℝ≥0∞ and
y : ℝ as the restriction of the real power function if 0 < x < ⊤, and with the natural values
for 0 and ⊤ (i.e., 0 ^ x = 0 for x > 0, 1 for x = 0 and ⊤ for x < 0, and
⊤ ^ x = 1 / 0 ^ x).
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Bundles fun x : ℝ≥0∞ => x ^ y into an order isomorphism when y : ℝ is positive,
where the inverse is fun x : ℝ≥0∞ => x ^ (1 / y).
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Positivity extension #
Extension for the positivity tactic: exponentiation by a real number is nonnegative when
the base is nonnegative and positive when the base is positive.
This is the NNReal analogue of evalRpow for Real.
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Extension for the positivity tactic: exponentiation by a real number is nonnegative when
the base is nonnegative and positive when the base is positive.
This is the ENNReal analogue of evalRpow for Real.
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NormNum extension for NNReal powers #
Given proofs
- that
ais a natural numberna; - that
bis a nonnegative rational numbernb / db; returns a tuple of - a natural number
r(result); - the same number, as an expression;
- a proof that
a ^ b = r.
Fails if na is not a dbth power of a natural number.
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Evaluates expressions of the form a ^ b when a : ℝ≥0 and b : ℝ.
Works if a, b, and a ^ b are in fact rational numbers.