dlang语言参考BigInt实现BigDecimal进行高精度计算

在D语言中，可以使用BigInt库来实现高精度计算，然后基于此实现BigDecimal。

导入BigInt库

import std.bigint;

定义BigDecimal类

class BigDecimal
{
    private BigInt _integerPart;
    private BigInt _decimalPart;
    private int _scale;

    public:
        // 构造函数
        this(BigInt integerPart, BigInt decimalPart, int scale)
        {
            _integerPart = integerPart;
            _decimalPart = decimalPart;
            _scale = scale;
        }

        // 加法运算
        BigDecimal opBinary(string op: "+")(in BigDecimal other)
        {
            auto maxScale = max(_scale, other._scale);
            auto integerPart = _integerPart + other._integerPart;
            auto decimalPart = _decimalPart * (BigInt(10) ^^ (maxScale - _scale))
                + other._decimalPart * (BigInt(10) ^^ (maxScale - other._scale));
            return BigDecimal(integerPart, decimalPart, maxScale);
        }

        // 减法运算
        BigDecimal opBinary(string op: "-")(in BigDecimal other)
        {
            auto maxScale = max(_scale, other._scale);
            auto integerPart = _integerPart - other._integerPart;
            auto decimalPart = _decimalPart * (BigInt(10) ^^ (maxScale - _scale))
                - other._decimalPart * (BigInt(10) ^^ (maxScale - other._scale));
            return BigDecimal(integerPart, decimalPart, maxScale);
        }

        // 乘法运算
        BigDecimal opBinary(string op: "*")(in BigDecimal other)
        {
            auto integerPart = _integerPart * other._integerPart;
            auto decimalPart = _decimalPart * other._decimalPart;
            auto scale = _scale + other._scale;
            return BigDecimal(integerPart, decimalPart, scale);
        }

        // 除法运算
        BigDecimal opBinary(string op: "/")(in BigDecimal other)
        {
            auto scale = max(_scale, other._scale);
            auto dividend = _integerPart * (BigInt(10) ^^ scale) + _decimalPart;
            auto divisor = other._integerPart * (BigInt(10) ^^ scale) + other._decimalPart;
            auto quotient = dividend / divisor;
            auto remainder = dividend % divisor;
            auto integerPart = quotient;
            auto decimalPart = remainder * (BigInt(10) ^^ (_scale + other._scale - scale * 2));
            return BigDecimal(integerPart, decimalPart, _scale + other._scale);
        }

        // 输出为字符串
        string toString()
        {
            auto scale = _scale;
            string decimalPartStr;
            while (scale > 0)
            {
                auto remainder = _decimalPart % 10;
                decimalPartStr = remainder.to!string ~ decimalPartStr;
                _decimalPart /= 10;
                scale--;
            }
            if (decimalPartStr.length > 0)
                decimalPartStr = "." ~ decimalPartStr;
            return _integerPart.to!string ~ decimalPartStr;
        }
}

使用BigDecimal类进行高精度计算

void main()
{
    auto a = BigDecimal(BigInt(123), BigInt(456), 2);
    auto b = BigDecimal(BigInt(789), BigInt(123), 3);
    auto c = a + b;
    auto d = a - b;
    auto e = a * b;
    auto f = a / b;
    writeln(a.toString()); // 输出 123.56
    writeln(b.toString()); // 输出 789.123
    writeln(c.toString()); // 输出 912.683
    writeln(d.toString()); // 输出 -665.563
    writeln(e.toString()); // 输出 97498.98888
    writeln(f.toString()); // 输出 0.1566628810198300302375809939
}
``