forked from mpusz/mp-units
96 lines
3.5 KiB
C++
96 lines
3.5 KiB
C++
// The MIT License (MIT)
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//
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// Copyright (c) 2018 Mateusz Pusz
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#include <mp-units/ostream.h>
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#include <mp-units/quantity.h>
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#include <mp-units/quantity_point.h>
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#include <iostream>
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#include <map>
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using namespace mp_units;
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// clang-format off
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inline constexpr struct dim_currency : base_dimension<"$"> {} dim_currency;
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QUANTITY_SPEC(currency, dim_currency);
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constexpr struct zero : absolute_point_origin<currency> {} zero;
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inline constexpr struct euro : named_unit<"EUR", kind_of<currency>> {} euro;
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inline constexpr struct us_dollar : named_unit<"USD", kind_of<currency>> {} us_dollar;
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inline constexpr struct great_british_pound : named_unit<"GBP", kind_of<currency>> {} great_british_pound;
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inline constexpr struct japanese_jen : named_unit<"JPY", kind_of<currency>> {} japanese_jen;
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// clang-format on
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static_assert(!std::equality_comparable_with<quantity<euro, int>, quantity<us_dollar, int>>);
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#if 0
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// if you have only a few currencies to handle
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template<Unit auto From, Unit auto To>
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[[nodiscard]] double exchange_rate()
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{
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if constexpr (From == us_dollar && To == euro) return 0.9215;
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else if constexpr (From == euro && To == us_dollar) return 1.0848;
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// ...
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}
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#else
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[[nodiscard]] std::string_view to_string_view(Unit auto u) { return u.symbol.ascii().c_str(); }
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template<Unit auto From, Unit auto To>
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[[nodiscard]] double exchange_rate()
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{
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static std::map<std::pair<std::string_view, std::string_view>, double> rates = {
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{{"USD", "EUR"}, 0.9215}, {{"EUR", "USD"}, 1.0848},
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// ...
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};
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return rates[std::make_pair(to_string_view(From), to_string_view(To))];
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}
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#endif
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template<ReferenceOf<currency> auto To, ReferenceOf<currency> auto From, typename Rep>
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quantity<To, Rep> exchange_to(quantity<From, Rep> q)
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{
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return static_cast<Rep>(exchange_rate<q.unit, get_unit(To)>() * q.value()) * To;
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}
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template<ReferenceOf<currency> auto To, ReferenceOf<currency> auto From, auto PO, typename Rep>
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quantity_point<To, PO, Rep> exchange_to(quantity_point<From, PO, Rep> q)
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{
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return quantity_point{
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zero + static_cast<Rep>(exchange_rate<q.unit, get_unit(To)>() * (q - q.absolute_point_origin).value()) * To};
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}
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int main()
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{
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quantity_point price_usd = zero + 100 * us_dollar;
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quantity_point price_euro = exchange_to<euro>(price_usd);
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std::cout << price_usd.quantity_from_origin() << " -> " << price_euro.quantity_from_origin() << "\n";
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// std::cout << price_usd.quantity_from_origin() + price_euro.quantity_from_origin() << "\n"; // does not compile
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}
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