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make fold.expresion.cpp work with negative values #268

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make fold.expresion.cpp work with negative values #268

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4 changes: 2 additions & 2 deletions exercises/2/fold.expresion.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,8 +11,8 @@
#include <iostream>
template<typename ... T>
auto average(T ... t) {
return (t + ... ) / sizeof...(t);
return static_cast<double>((t + ... )) / sizeof...(t);
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我个人建议是模仿 <cmath> 中浮点函数的额外重载，把整数类型转换为 double 而浮点类型不变。这样可以避免 long double 被转换为 double。

Suggested change
return static_cast<double>((t + ... )) / sizeof...(t);
constexpr auto integer_to_double = [](auto x) {
if constexpr (std::is_integral_v<decltype(x)>)
return static_cast<double>(x);
else
return x;
};
return (integer_to_double(t) + ... ) / sizeof...(t);

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static_caste() it will explicitly change the data type of t to double

#include <iostream>

template<typename ... T>
auto average(T ... t) {
    return (static_cast<double>(t) + ...) / sizeof...(t);
}

int main() {
    std::cout << average(1, 2, 3, 4, 5, -6, -7, -8, -9, -10) << std::endl;
}
}

}
int main() {
std::cout << average(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
}
}