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implementing our own (very limited) std::pow functions

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integer and float treated separately
perhaps not ideal, but not obvioius what would be clearly better
This commit is contained in:
Oliver Schönrock
2019-12-28 13:12:39 +00:00
committed by Mateusz Pusz
parent 0ad78fe753
commit 23d44c1b4a
2 changed files with 51 additions and 9 deletions
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6
src/include/units/quantity.h
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@@ -353,7 +353,11 @@ template<typename D1, typename U1, typename Rep1, typename D2, typename U2, type
{
using common_rep = decltype(lhs.count() * rhs.count());
using ratio = ratio_multiply<typename U1::ratio, typename U2::ratio>;
return common_rep(lhs.count()) * common_rep(rhs.count()) * common_rep(ratio::num) * std::pow(10, common_rep(ratio::exp)) / common_rep(ratio::den);
if constexpr (treat_as_floating_point<common_rep>) {
return common_rep(lhs.count()) * common_rep(rhs.count()) * common_rep(ratio::num) * fpow10(ratio::exp) / common_rep(ratio::den);
} else {
return common_rep(lhs.count()) * common_rep(rhs.count()) * common_rep(ratio::num) * ipow10(ratio::exp) / common_rep(ratio::den);
}
}
template<typename D1, typename U1, typename Rep1, typename D2, typename U2, typename Rep2>

54
src/include/units/quantity_cast.h
View File

@@ -24,10 +24,40 @@
#include <units/concepts.h>
#include <units/bits/dimension_op.h>
#include <cmath>
namespace units {
constexpr std::intmax_t ipow10(std::intmax_t exp) {
// how to assert here?
// static_assert(exp >= 0, "Use fpow10() for negative exponents");
if (exp == 0) return 1;
std::intmax_t result = 1;
while (exp > 0) {
result *= 10;
--exp;
}
return result;
}
constexpr long double fpow10(std::intmax_t exp) {
if (exp == 0) return 1.0L;
long double result = 1.0L;
if (exp < 0) {
while (exp < 0) {
result /= 10.0L;
++exp;
}
} else {
while (exp > 0) {
result *= 10.0L;
--exp;
}
}
return result;
}
// QuantityOf
template<typename T, typename Dim>
concept QuantityOf = Quantity<T> && Dimension<Dim> && equivalent_dim<typename T::dimension, Dim>;
@@ -42,15 +72,15 @@ struct quantity_cast_impl {
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
static_cast<CRep>(std::pow(10, CRatio::exp)) *
static_cast<CRep>(fpow10(CRatio::exp)) *
(static_cast<CRep>(CRatio::num) /
static_cast<CRep>(CRatio::den))));
} else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
static_cast<CRep>(CRatio::num) *
static_cast<CRep>(CRatio::exp > 0 ? std::pow(10, CRatio::exp) : 1) /
static_cast<CRep>(CRatio::exp > 0 ? ipow10(CRatio::exp) : 1) /
(static_cast<CRep>(CRatio::den) *
static_cast<CRep>(CRatio::exp < 0 ? std::pow(10, -CRatio::exp) : 1))));
static_cast<CRep>(CRatio::exp < 0 ? ipow10(-CRatio::exp) : 1))));
}
}
};
@@ -60,7 +90,11 @@ struct quantity_cast_impl<To, CRatio, CRep, true, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(std::pow(10, CRatio::exp))));
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(fpow10(CRatio::exp))));
} else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(ipow10(CRatio::exp))));
}
}
};
@@ -70,9 +104,9 @@ struct quantity_cast_impl<To, CRatio, CRep, true, false> {
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(std::pow(10, CRatio::exp)) * (CRep{1} / static_cast<CRep>(CRatio::den))));
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(fpow10(CRatio::exp)) * (CRep{1} / static_cast<CRep>(CRatio::den))));
} else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(std::pow(10, CRatio::exp)) / static_cast<CRep>(CRatio::den)));
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(ipow10(CRatio::exp)) / static_cast<CRep>(CRatio::den)));
}
}
};
@@ -82,7 +116,11 @@ struct quantity_cast_impl<To, CRatio, CRep, false, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) * static_cast<CRep>(std::pow(10, CRatio::exp))));
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) * static_cast<CRep>(fpow10(CRatio::exp))));
} else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) * static_cast<CRep>(ipow10(CRatio::exp))));
}
}
};