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Currency rate: Compute how many decimals we need to display two meaningful digits at minimum

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This commit is contained in:
Rudy Huyn 2019-03-10 19:48:14 -07:00
commit e59a67fa98
3 changed files with 61 additions and 15 deletions
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31
src/CalcViewModel/DataLoaders/CurrencyDataLoader.cpp
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@ -1,4 +1,4 @@
// Copyright (c) Microsoft Corporation. All rights reserved.
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
#include "pch.h"
@ -40,6 +40,8 @@ static constexpr long long DAY_DURATION = 1LL * 60 * 60 * 24 * 10000000;
static constexpr long long WEEK_DURATION = DAY_DURATION * 7;
static constexpr int FORMATTER_DIGIT_COUNT = 4;
static constexpr int FORMATTER_RATE_MIN_DIGIT_COUNT = 4;
static constexpr int FORMATTER_RATE_MIN_MEANINGFULL_DIGITS = 2;
static constexpr auto CACHE_TIMESTAMP_KEY = L"CURRENCY_CONVERTER_TIMESTAMP";
static constexpr auto CACHE_LANGCODE_KEY = L"CURRENCY_CONVERTER_LANGCODE";
@ -262,6 +264,23 @@ pair<wstring, wstring> CurrencyDataLoader::GetCurrencySymbols(const UCM::Unit& u
return make_pair(symbol1, symbol2);
}
double CurrencyDataLoader::RoundCurrencyRatio(double ratio)
{
// Compute how many decimals we need to display two meaningful digits at minimum
// For example: 0.000000003423 -> 0.0000000034, 0.000212 -> 0.00021
int numberDecimals = FORMATTER_RATE_MIN_DIGIT_COUNT;
if (ratio < 1)
{
numberDecimals = max(
FORMATTER_RATE_MIN_DIGIT_COUNT,
(int)(-log10(ratio)) + FORMATTER_RATE_MIN_MEANINGFULL_DIGITS);
}
unsigned long long scale = (unsigned long long)powl(10l, numberDecimals);
return (double)(round(ratio * scale) / scale);
}
pair<wstring, wstring> CurrencyDataLoader::GetCurrencyRatioEquality(_In_ const UCM::Unit& unit1, _In_ const UCM::Unit& unit2)
{
try
@ -274,16 +293,10 @@ pair<wstring, wstring> CurrencyDataLoader::GetCurrencyRatioEquality(_In_ const U
if (iter2 != ratioMap.end())
{
double ratio = (iter2->second).ratio;
// Round the ratio to FORMATTER_DIGIT_COUNT digits using int math.
// Ex: to round 1.23456 to three digits, use
// ((int) 1.23456 * (10^3)) / (10^3)
double scale = pow(10, FORMATTER_DIGIT_COUNT);
double rounded = static_cast<int>(ratio * static_cast<int>(scale)) / scale;
double rounded = RoundCurrencyRatio(ratio);
wstring roundedFormat = m_ratioFormatter->Format(rounded)->Data();;
wstring digitSymbol = wstring{ LocalizationSettings::GetInstance().GetDigitSymbolFromEnUsDigit(L'1') };
wstring roundedFormat = m_ratioFormatter->Format(rounded)->Data();
wstring ratioString = LocalizationStringUtil::GetLocalizedString(
m_ratioFormat.c_str(),
digitSymbol.c_str(),

3
src/CalcViewModel/DataLoaders/CurrencyDataLoader.h
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@ -1,4 +1,4 @@
// Copyright (c) Microsoft Corporation. All rights reserved.
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
#pragma once
@ -71,6 +71,7 @@ namespace CalculatorApp
std::pair<std::wstring, std::wstring> GetCurrencySymbols(const UCM::Unit& unit1, const UCM::Unit& unit2) override;
std::pair<std::wstring, std::wstring> GetCurrencyRatioEquality(_In_ const UnitConversionManager::Unit& unit1, _In_ const UnitConversionManager::Unit& unit2) override;
std::wstring GetCurrencyTimestamp() override;
static double RoundCurrencyRatio(double ratio);
concurrency::task<bool> TryLoadDataFromCacheAsync() override;
concurrency::task<bool> TryLoadDataFromWebAsync() override;

34
src/CalculatorUnitTests/CurrencyConverterUnitTests.cpp
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@ -1,4 +1,4 @@
// Copyright (c) Microsoft Corporation. All rights reserved.
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
#include "pch.h"
@ -597,5 +597,37 @@ namespace CalculatorUnitTests
VERIFY_ARE_EQUAL(wstring(L""), ratio.first);
VERIFY_ARE_EQUAL(wstring(L""), ratio.second);
}
TEST_METHOD(Test_RoundCurrencyRatio)
{
CurrencyDataLoader loader{ nullptr };
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(1234567), 1234567);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0), 0);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(9999.999), 9999.999);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(8765.4321), 8765.4321);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(4815.162342), 4815.1623);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(4815.162358), 4815.1624);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(4815.162388934723), 4815.1624);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.12), 0.12);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.123), 0.123);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.1234), 0.1234);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.12343), 0.1234);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0321), 0.0321);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.03211), 0.0321);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.03219), 0.0322);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.003219), 0.0032);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.003269), 0.0033);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.000269), 0.00027);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.000069), 0.000069);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.000061), 0.000061);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000612), 0.000061);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000616), 0.000062);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000016), 0.0000016);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000016134324), 0.0000016);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000096134324), 0.0000096);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.00000169348392), 0.0000017);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000000034987218), 0.0000000035);
VERIFY_ARE_EQUAL(CurrencyDataLoader::RoundCurrencyRatio(0.0000000000000231445), 0.000000000000023);
}
};
}