关于+=运算符重载的问题
为啥cout<<c2+=5;编译要报错，而写成c2+=5;cout<<c2;就没错？
以下是正确的代码 是c2+=5;cout<<c2; 就是不知道为啥写成cout<<c2+=5;时编译要报错
#include <iostream.h>
#include <stdlib.h>
int Days[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int Days2[14]={0,31,31,28,31,30,31,30,31,31,30,31,30,31};
class CDate
{
public:
CDate(int year=2013,int month=1,int day=1):Year(year),Month(month),Day(day){}
bool IsLeapYear(int year);
void SetTime();
CDate &operator++();
CDate operator++(int);
CDate &operator--();
CDate operator--(int);
CDate &operator+=(int right);
CDate &operator-=(int right);
friend CDate operator+(const CDate &c,int x);
friend CDate operator-(const CDate &c,int x);
friend istream &operator>>(istream &input,CDate &c);
friend ostream &operator<<(ostream &output,const CDate &c);
friend bool operator==(const CDate &c1,const CDate &c2);
friend bool operator!=(const CDate &c1,const CDate &c2);
friend bool operator<(const CDate &c1,const CDate &c2);
friend bool operator>(const CDate &c1,const CDate &c2);
friend bool operator<=(const CDate &c1,const CDate &c2);
friend bool operator>=(const CDate &c1,const CDate &c2);
private:
int Year,Month,Day;
};
bool CDate::IsLeapYear(int year)
{
return ((year%4==0&&year%100!=0)||year%400==0);
}
void CDate::SetTime()
{
cout<<"Please enter a date:";
cin>>Year>>Month>>Day;
if (IsLeapYear(Year))
Days[2]=29;
if (Month<1||Month>12)
{
cout<<"The date is not valid"<<endl;
exit(1);
}
if (Day<1||Day>Days[Month])
{
cout<<"The date is not valid."<<endl;
exit(1);
}
cout<<"Set the date successfully!"<<endl;
}
CDate &CDate::operator++()
{
Day++;
if (IsLeapYear(Year))
Days[2]=29;
else
Days[2]=28;
if (Day>Days[Month])
{
Month++;
Day=1;
if (Month>12)
{
Month=1;
Year++;
}
}
return *this;
}
CDate CDate::operator++(int)
{
CDate old=*this;
++(*this);
return old;
}
CDate &CDate::operator--()
{
Day--;
if (IsLeapYear(Year))
Days[2]=29;
else
Days[2]=28;
if (Day==0)
{
Month--;
if (Month==0)
{
Month=12;
Year--;
}
Day=Days[Month];
}
return *this;
}
CDate CDate::operator--(int)
{
CDate old=*this;
--(*this);
return old;
}
CDate &CDate::operator+=(int right)
{
Day+=right;
while (Day>Days[Month])
{
if (IsLeapYear(Year))
Days[2]=29;
else
Days[2]=28;
Day-=Days[Month];
Month++;
if (Month>12)
{
Month=1;
Year++;
}
}
return *this;
}
CDate &CDate::operator-=(int right)
{
Day-=right;
while (Day<=0)
{
if (IsLeapYear(Year))
Days[2]=29;
else
Days[2]=28;
Day+=Days[Month];
Month--;
if (Month==0)
{
Month=12;
Year--;
}
}
return *this;
}
CDate operator+(const CDate &c,int x)
{
CDate temp=c;
temp.Day+=x;
while (temp.Day>Days[temp.Month])
{
if (temp.IsLeapYear(temp.Year))
Days[2]=29;
else
Days[2]=28;
temp.Day-=Days[temp.Month];
temp.Month++;
if (temp.Month>12)
{
temp.Month=1;
temp.Year++;
}
}
return temp;
}
CDate operator-(const CDate &c,int x)
{
CDate temp=c;
temp.Day-=x;
while (temp.Day<=0)
{
if (temp.IsLeapYear(temp.Year))
Days2[3]=29;
else
Days2[3]=28;
temp.Day+=Days2[temp.Month];
temp.Month--;
if (temp.Month==0)
{
temp.Month=12;
temp.Year--;
}
}
return temp;
}
istream &operator>>(istream &input,CDate &c)
{
input>>c.Year>>c.Month>>c.Day;
return input;
}
ostream &operator<<(ostream &output,const CDate &c)
{
output<<c.Year<<"/"<<c.Month<<"/"<<c.Day<<endl;
return output;
}
bool operator==(const CDate &c1,const CDate &c2)
{
if (c1.Year==c2.Year&&c1.Month==c2.Month&&c1.Day==c2.Day)
return true;
else
return false;
}
bool operator!=(const CDate &c1,const CDate &c2)
{
if (c1.Year!=c2.Year||c1.Month!=c2.Month||c1.Day!=c2.Day)
return true;
else
return false;
}
bool operator<(const CDate &c1,const CDate &c2)
{
if (c1.Year<c2.Year)
return true;
else if (c1.Year>c2.Year)
return false;
else
{
if (c1.Month<c2.Month)
return true;
else if (c1.Month>c2.Month)
return false;
else
{
if (c1.Day<c2.Day)
return true;
else
return false;
}
}
}
bool operator>(const CDate &c1,const CDate &c2)
{
if (c1.Year>c2.Year)
return true;
else if (c1.Year<c2.Year)
return false;
else
{
if (c1.Month>c2.Month)
return true;
else if (c1.Month<c2.Month)
return false;
else
{
if (c1.Day>c2.Day)
return true;
else
return false;
}
}
}
bool operator<=(const CDate &c1,const CDate &c2)
{
if (c1.Year<c2.Year)
return true;
else if (c1.Year>c2.Year)
return false;
else
{
if (c1.Month<c2.Month)
return true;
else if (c1.Month>c2.Month)
return false;
else
{
if (c1.Day<=c2.Day)
return true;
else
return false;
}
}
}
bool operator>=(const CDate &c1,const CDate &c2)
{
if (c1.Year>c2.Year)
return true;
else if (c1.Year<c2.Year)
return false;
else
{
if (c1.Month>c2.Month)
return true;
else if (c1.Month<c2.Month)
return false;
else
{
if (c1.Day>=c2.Day)
return true;
else
return false;
}
}
}
void main()
{
CDate c1,c2;
c1.SetTime();
cout<<c1++;
cout<<++c1;
cout<<c1--;
cout<<--c1;
cin>>c2;
cout<<c2+300;
cout<<c2-300;
c2+=5;
cout<<c2;
c2-=5;
cout<<c2;
if (c1==c2)
cout<<"c1=c2"<<endl;
else
cout<<"c1!=c2"<<endl;
if (c1!=c2)
cout<<"c1!=c2"<<endl;
else
cout<<"c1=c2"<<endl;
if (c1>c2)
cout<<"c1>c2"<<endl;
else
cout<<"c1<=c2"<<endl;
if (c1<c2)
cout<<"c1<c2"<<endl;
else
cout<<"c1>=c2"<<endl;
if (c1>=c2)
cout<<"c1>=c2"<<endl;
else
cout<<"c1<c2"<<endl;
if (c1<=c2)
cout<<"c1<=c2"<<endl;
else
cout<<"c1>c2"<<endl;
}
//C++ Operators
// Operators specify an evaluation to be performed on one of the following:
// One operand (unary operator)
// Two operands (binary operator)
// Three operands (ternary operator)
// The C++ language includes all C operators and adds several new operators.
// Table 1.1 lists the operators available in Microsoft C++.
// Operators follow a strict precedence which defines the evaluation order of
//expressions containing these operators. Operators associate with either the
//expression on their left or the expression on their right; this is called
//“associativity.” Operators in the same group have equal precedence and are
//evaluated left to right in an expression unless explicitly forced by a pair of
//parentheses, ( ).
// Table 1.1 shows the precedence and associativity of C++ operators
// (from highest to lowest precedence).
//
//Table 1.1 C++ Operator Precedence and Associativity
// The highest precedence level is at the top of the table.
//+------------------+-----------------------------------------+---------------+
//
[解决办法]
Operator
[解决办法]
Name or Meaning
[解决办法]
Associativity
[解决办法]
//+------------------+-----------------------------------------+---------------+
//
[解决办法]
::
[解决办法]
Scope resolution
[解决办法]
None
[解决办法]
//
[解决办法]
::
[解决办法]
Global
[解决办法]
None
[解决办法]
//
[解决办法]
[ ]
[解决办法]
Array subscript
[解决办法]
Left to right
[解决办法]
//
[解决办法]
( )
[解决办法]
Function call
[解决办法]
Left to right
[解决办法]
//
[解决办法]
( )
[解决办法]
Conversion
[解决办法]
None
[解决办法]
//
[解决办法]
.
[解决办法]
Member selection (object)
[解决办法]
Left to right
[解决办法]
//
[解决办法]
->
[解决办法]
Member selection (pointer)
[解决办法]
Left to right
[解决办法]
//
[解决办法]
++
[解决办法]
Postfix increment
[解决办法]
None
[解决办法]
//
[解决办法]
--
[解决办法]
Postfix decrement
[解决办法]
None
[解决办法]
//
[解决办法]
new
[解决办法]
Allocate object
[解决办法]
None
[解决办法]
//
[解决办法]
delete
[解决办法]
Deallocate object
[解决办法]
None
[解决办法]
//
[解决办法]
delete[ ]
[解决办法]
Deallocate object
[解决办法]
None
[解决办法]
//
[解决办法]
++
[解决办法]
Prefix increment
[解决办法]
None
[解决办法]
//
[解决办法]
--
[解决办法]
Prefix decrement
[解决办法]
None
[解决办法]
//
[解决办法]
*
[解决办法]
Dereference
[解决办法]
None
[解决办法]
//
[解决办法]
&
[解决办法]
Address-of
[解决办法]
None
[解决办法]
//
[解决办法]
+
[解决办法]
Unary plus
[解决办法]
None
[解决办法]
//
[解决办法]
-
[解决办法]
Arithmetic negation (unary)
[解决办法]
None
[解决办法]
//
[解决办法]
!
[解决办法]
Logical NOT
[解决办法]
None
[解决办法]
//
[解决办法]
~
[解决办法]
Bitwise complement
[解决办法]
None
[解决办法]
//
[解决办法]
sizeof
[解决办法]
Size of object
[解决办法]
None
[解决办法]
//
[解决办法]
sizeof ( )
[解决办法]
Size of type
[解决办法]
None
[解决办法]
//
[解决办法]
typeid( )
[解决办法]
type name
[解决办法]
None
[解决办法]
//
[解决办法]
(type)
[解决办法]
Type cast (conversion)
[解决办法]
Right to left
[解决办法]
//
[解决办法]
const_cast
[解决办法]
Type cast (conversion)
[解决办法]
None
[解决办法]
//
[解决办法]
dynamic_cast
[解决办法]
Type cast (conversion)
[解决办法]
None
[解决办法]
//
[解决办法]
reinterpret_cast
[解决办法]
Type cast (conversion)
[解决办法]
None
[解决办法]
//
[解决办法]
static_cast
[解决办法]
Type cast (conversion)
[解决办法]
None
[解决办法]
//
[解决办法]
.*
[解决办法]
Apply pointer to class member (objects)
[解决办法]
Left to right
[解决办法]
//
[解决办法]
->*
[解决办法]
Dereference pointer to class member
[解决办法]
Left to right
[解决办法]
//
[解决办法]
*
[解决办法]
Multiplication
[解决办法]
Left to right
[解决办法]
//
[解决办法]
/
[解决办法]
Division
[解决办法]
Left to right
[解决办法]
//
[解决办法]
%
[解决办法]
Remainder (modulus)
[解决办法]
Left to right
[解决办法]
//
[解决办法]
+
[解决办法]
Addition
[解决办法]
Left to right
[解决办法]
//
[解决办法]
-
[解决办法]
Subtraction
[解决办法]
Left to right
[解决办法]
//
[解决办法]
<<
[解决办法]
Left shift
[解决办法]
Left to right
[解决办法]
//
[解决办法]
>>
[解决办法]
Right shift
[解决办法]
Left to right
[解决办法]
//
[解决办法]
<
[解决办法]
Less than
[解决办法]
Left to right
[解决办法]
//
[解决办法]
>
[解决办法]
Greater than
[解决办法]
Left to right
[解决办法]
//
[解决办法]
<=
[解决办法]
Less than or equal to
[解决办法]
Left to right
[解决办法]
//
[解决办法]
>=
[解决办法]
Greater than or equal to
[解决办法]
Left to right
[解决办法]
//
[解决办法]
==
[解决办法]
Equality
[解决办法]
Left to right
[解决办法]
//
[解决办法]
!=
[解决办法]
Inequality
[解决办法]
Left to right
[解决办法]
//
[解决办法]
&
[解决办法]
Bitwise AND
[解决办法]
Left to right
[解决办法]
//
[解决办法]
^
[解决办法]
Bitwise exclusive OR
[解决办法]
Left to right
[解决办法]
//
[解决办法]
[解决办法]
[解决办法]
Bitwise OR
[解决办法]
Left to right
[解决办法]
//
[解决办法]
&&
[解决办法]
Logical AND
[解决办法]
Left to right
[解决办法]
//
[解决办法]
[解决办法]
[解决办法]
Logical OR
[解决办法]
Left to right
[解决办法]
//
[解决办法]
e1?e2:e3
[解决办法]
Conditional
[解决办法]
Right to left
[解决办法]
//
[解决办法]
=
[解决办法]
Assignment
[解决办法]
Right to left
------解决方案--------------------
//
[解决办法]
*=
[解决办法]
Multiplication assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
/=
[解决办法]
Division assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
%=
[解决办法]
Modulus assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
+=
[解决办法]
Addition assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
-=
[解决办法]
Subtraction assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
<<=
[解决办法]
Left-shift assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
>>=
[解决办法]
Right-shift assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
&=
[解决办法]
Bitwise AND assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
[解决办法]
=
[解决办法]
Bitwise inclusive OR assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
^=
[解决办法]
Bitwise exclusive OR assignment
[解决办法]
Right to left
[解决办法]
//
[解决办法]
,
[解决办法]
Comma
[解决办法]
Left to right
------解决方案--------------------
//+------------------+-----------------------------------------+---------------+
