浅谈 C++ 类语法

1234567class UserClass
{
    public:
        void Debug(int Time)
      
{
            <具体实现>
       }
};

12345678class UserClass
{
    public:
        void Debug(int Time);
};
void UserClass::Debug(int Time)
{
    <具体实现>
}

void Function(UsClass &&Obj,...)

1234567std::move()//左值转右值
//std::forward() 才是完美转发,感谢各路大佬指出!
//定义头长这样，头疼就跳过！
template<typename T>
constexpr typename std::remove_reference<T>::type&& move(T&& t)noexcept
{
    return static_cast<typename std::remove_reference<T>::type&&>(t);
}//自行查资料理解，此处不予解释。

12345class UserClass
{
    template<typename<类型名>>
    <类型名><方法名>();
};

123456[[noreturn]]void SysExit()
{
    exit(0);
}
int main()
{
    SysExit();
}

123456[[nodiscard]]void UnUsedRetrnFunc()
{
    return 42;//编译器会发出警告！
}
int main()
{
    UnUsedRetrnFunc();
}

123456[[deprecated("Used New ...")]]void OldFunc()
{
    return 42;
}
int main()
{
    OldFunc();//编译器会发出警告！
}

12345678if(condition)[[likely]]
{
    // 高概率执行的代码
}
else[[unlikely]]
{
    // 低概率执行的代码
}

123456789101112131415161718192021String::String()noexcept:Data(new char[1]{'\0'})Len(0){}
String::String(const char* CStringing)
{
    Len=strlen(CString);
    Data=new char[Len+1];
    std::copy(CString, CString+Len+1, Data);
}
String::String(const String& Other):Len(Other.Len)
{
    Data=new char[Len+1];
    std::copy(Other.Data, Other.Data+Len+1, Data);
}
String::String(String&& Other)noexcept:Data(Other.Data), Len(Other.Len)
{
    Other.Data=nullptr;
    Other.Len=0;
}
String::~String()
{
    delete[] Data;
}

1234567891011121314151617181920212223242526272829303132333435363738String& String::operator=(const String& Other)
{
    if(this!=&Other)
    {
        char* new_data=new char[Other.Len+1];
        std::copy(Other.Data, Other.Data+Other.Len+1, new_data);
        delete[] Data;
        Data=new_data;
        Len=Other.Len;
    }
    return *this;
}
String& String::operator=(String&& Other)noexcept
{
    if(this!=&Other)
    {
        delete[] Data;
        Data=Other.Data;
        Len=Other.Len;
        Other.Data=nullptr;
        Other.Len=0;
    }
    return *this;
}
bool operator==(const String& Other)const
{
    return strcmp(Data, Other.Data)==0;
}
char& operator[](int Index)
{
    if(Index<0||Index>=Len)throw std::out_of_range("Index out of range");
    return Data[Index];
}
const char& operator[](int Index)const
{
    if(Index<0||Index>=Len)throw std::out_of_range("Index out of range");
    return Data[Index];
}

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475int Find(const String& Sub)const
{
    if(Sub.Len==0)return 0;
    for(int Index=0; Index <= Len-Sub.Len; ++Index)
    {
        bool Match=true;
        for(int TmpInd=0; TmpInd<Sub.Len; ++TmpInd)
        {
            if(Data[Index+TmpInd]!=Sub.Data[TmpInd])
            {
                Match=false;
                break;
            }
        }
        if(Match)return Index;
    }
    return -1;
}
String Replace(const String& Sub, const String& Replacement)const
{
    std::vector<int>Positions;
    int SubLen=Sub.Len;
    if(SubLen==0)return *this;
    int Pos=0;
    while(Pos<=Len-SubLen)
    {
        bool Found=true;
        for(int Index=0;Index<SubLen;++Index)
        {
            if(Data[Pos+Index]!=Sub.Data[Index])
            {
                Found=false;
                break;
            }
        }
        if(Found)
        {
            Positions.push_back(Pos);
            Pos+=SubLen;
        }
        else
        {
            Pos++;
        }
    }
    int NewLen=Len+Positions.size()*(Replacement.Len-SubLen);
    String Result;
    delete[] Result.Data;
    Result.Data=new char[NewLen+1];
    Result.Len=NewLen;
    int SourcePos=0;
    int DetectPos=0;
    for(int Pos:Positions)
    {
        int CopyLen=Pos-SourcePos;
        std::copy(Data+SourcePos, Data+SourcePos+CopyLen, Result.Data+DetectPos);
        DetectPos+=CopyLen;
        std::copy(Replacement.Data, Replacement.Data+Replacement.Len, Result.Data+DetectPos);
        DetectPos+=Replacement.Len;
        SourcePos=Pos+SubLen;
    }
    std::copy(Data+SourcePos, Data+Len, Result.Data+DetectPos);
    Result.Data[NewLen]='\0';
    return Result;
}
String Silce(int Left, int Right)
{
    if(Left<0)Left=0;
    if(Right>Len)Right=Len;
    if(Left>=Right)return String();
    String Result;
    Result.Len=Right-Left;
    delete[] Result.Data;
    Result.Data=new char[Result.Len+1];
    std::copy(Data+Left, Data+Right, Result.Data);
    Result.Data[Result.Len]='\0';
    return Result;
}