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98 lines
2.3 KiB
Markdown
98 lines
2.3 KiB
Markdown
---
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title: "ratio"
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---
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{{< callout type="info">}}
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Header: `ratio.h`
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Since: `TBC`
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Similar to: [std::ratio](https://en.cppreference.com/w/cpp/numeric/ratio/ratio)
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{{< /callout >}}
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A template constant to encode ratios.
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```cpp
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template <const size_t NUM, const size_t DEN = 1>
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struct ratio
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{
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static ETL_CONSTANT intmax_t num = NUM;
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static ETL_CONSTANT intmax_t den = DEN;
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};
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```
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`num` : Numerator
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`den` : Denominator
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## Predefined ratios
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If `INT_MAX` > `INT32_MAX`
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```cpp
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typedef ratio<1, 1000000000000000000LL * 1000000000000LL> quecto;
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typedef ratio<1, 1000000000000000000LL * 1000000000LL> ronto;
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typedef ratio<1, 1000000000000000000000000LL> yocto;
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typedef ratio<1, 1000000000000000000000> zepto;
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typedef ratio<1, 1000000000000000000> atto;
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typedef ratio<1, 1000000000000000> femto;
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typedef ratio<1, 1000000000000> pico;
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```
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If `INT_MAX` >= `INT32_MAX`
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```cpp
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typedef ratio<1, 1000000000> nano;
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typedef ratio<1, 1000000> micro;
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```
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If `INT_MAX` >= `INT16_MAX`
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```cpp
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typedef ratio<1, 1000> milli;
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typedef ratio<1, 100> centi;
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typedef ratio<1, 10> deci;
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typedef ratio<10, 1> deca;
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typedef ratio<100, 1> hecto;
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typedef ratio<1000, 1> kilo;
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```
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If `INT_MAX` >= `INT32_MAX`
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```cpp
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typedef ratio<1000000, 1> mega;
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typedef ratio<1000000000, 1> giga;
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```
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If `INT_MAX` > `INT32_MAX`
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```cpp
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typedef ratio<1000000000000, 1> tera;
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typedef ratio<1000000000000000, 1> peta;
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typedef ratio<1000000000000000000, 1> exa;
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typedef ratio<1000000000000000000000, 1> zetta;
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typedef ratio<1000000000000000000000000LL, 1> yotta;
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typedef ratio<1000000000000000000LL * 1000000000LL, 1> ronna;
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typedef ratio<1000000000000000000LL * 1000000000000LL, 1> quetta;
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```
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---
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```cpp
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typedef ratio<355, 113> ratio_pi;
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```
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An approximation of PI to 6 digits.
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---
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```cpp
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typedef ratio<239, 169> ratio_root2;
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```
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An approximation of root 2.
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---
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```cpp
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typedef ratio<169, 239> ratio_1_over_root2;
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```
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An approximation of 1 over root 2.
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---
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```cpp
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typedef ratio<326, 120> ratio_e;
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```
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An approximation of e.
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