電卓 - Siv3D/Reference-JP GitHub Wiki

# include <Siv3D.hpp>

void Main()
{
    Graphics::SetBackground(Color(240));

    const Font font(40);

    String expression;

    while (System::Update())
    {
        Input::GetCharsHelper(expression);

        font(expression).draw(10, 10, Palette::Black);

        if (const auto result = EvaluateOpt(expression))
        {
            font(result.value()).draw(10, 250, Palette::Black);
        }
    }
}