read this article -> http://www.functionx.com/cpp/keywords/typedef.htm
It said that "The typedef keyword can be followed by an attribute before the data type. In its simplest form, the attribute can be that of an access level such as public, private, or protected." and provide a examples:
#include <iostream>
#include <string>
using namespace std;
typedef struct Student;
typedef class Country;
typedef public short SmallNumber;
typedef private unsigned int Positive;
typedef protected double* PDouble;
typedef public string FiveStrings[5];
typedef private double (*Addition)(double value1, double value2);
struct Student
{
string FirstName;
string LastName;
};
typedef struct _Empl
{
string FullName;
double HourlySalary;
}Employee;
class Country
{
string Name;
string Capital;
string Code;
};
double Add(double x, double y)
{
double result = x + y;
return result;
}
typedef enum EmplStatus { esFullTime, esPartTime, esContractor };
typedef Student *PStudent;
typedef Country *PCountry;
int main()
{
Student pupil;
Country pais;
EmplStatus emplst;
PStudent ptrStd = new Student;
PCountry pPais = new Country;
return 0;
}
I found that I can't compile it on my Linux using g++.
[root@sd1 xxx]# g++ typedef.cpp -o typedef
typedef.cpp:8: error: expected unqualified-id before 'public'
typedef.cpp:9: error: expected unqualified-id before 'private'
typedef.cpp:10: error: expected unqualified-id before 'protected'
typedef.cpp:11: error: expected unqualified-id before 'public'
typedef.cpp:12: error: expected unqualified-id before 'private'
Why, can anybody tell me?
:)
C++ operator precedence
http://www.cppreference.com/operator_precedence.html| Precedence | Operator | Description | Example | Associativity |
|---|
| 1 | ()
[]
->
.
::
++
-- | Grouping operator
Array access
Member access from a pointer
Member access from an object
Scoping operator
Post-increment
Post-decrement | (a + b) / 4;
array[4] = 2;
ptr->age = 34;
obj.age = 34;
Class::age = 2;
for( i = 0; i < 10; i++ ) ...
for( i = 10; i > 0; i-- ) ... | left to right |
| 2 | !
~
++
--
-
+
*
&
(type)
sizeof | Logical negation
Bitwise complement
Pre-increment
Pre-decrement
Unary minus
Unary plus
Dereference
Address of
Cast to a given type
Return size in bytes | if( !done ) ...
flags = ~flags;
for( i = 0; i < 10; ++i ) ...
for( i = 10; i > 0; --i ) ...
int i = -1;
int i = +1;
data = *ptr;
address = &obj;
int i = (int) floatNum;
int size = sizeof(floatNum); | right to left |
| 3 | ->*
.* | Member pointer selector
Member pointer selector | ptr->*var = 24;
obj.*var = 24; | left to right |
| 4 | *
/
% | Multiplication
Division
Modulus | int i = 2 * 4;
float f = 10 / 3;
int rem = 4 % 3; | left to right |
| 5 | +
- | Addition
Subtraction | int i = 2 + 3;
int i = 5 - 1; | left to right |
| 6 | <<
>> | Bitwise shift left
Bitwise shift right | int flags = 33 << 1;
int flags = 33 >> 1; | left to right |
| 7 | <
<=
>
>= | Comparison less-than
Comparison less-than-or-equal-to
Comparison greater-than
Comparison geater-than-or-equal-to | if( i < 42 ) ...
if( i <= 42 ) ...
if( i > 42 ) ...
if( i >= 42 ) ... | left to right |
| 8 | ==
!= | Comparison equal-to
Comparison not-equal-to | if( i == 42 ) ...
if( i != 42 ) ... | left to right |
| 9 | & | Bitwise AND | flags = flags & 42; | left to right |
| 10 | ^ | Bitwise exclusive OR | flags = flags ^ 42; | left to right |
| 11 | | | Bitwise inclusive (normal) OR | flags = flags | 42; | left to right |
| 12 | && | Logical AND | if( conditionA && conditionB ) ... | left to right |
| 13 | || | Logical OR | if( conditionA || conditionB ) ... | left to right |
| 14 | ? : | Ternary conditional (if-then-else) | int i = (a > b) ? a : b; | right to left |
| 15 | =
+=
-=
*=
/=
%=
&=
^=
|=
<<=
>>= | Assignment operator
Increment and assign
Decrement and assign
Multiply and assign
Divide and assign
Modulo and assign
Bitwise AND and assign
Bitwise exclusive OR and assign
Bitwise inclusive (normal) OR and assign
Bitwise shift left and assign
Bitwise shift right and assign | int a = b;
a += 3;
b -= 4;
a *= 5;
a /= 2;
a %= 3;
flags &= new_flags;
flags ^= new_flags;
flags |= new_flags;
flags <<= 2;
flags >>= 2; | right to left |
| 16 | , | Sequential evaluation operator | for( i = 0, j = 0; i < 10; i++, j++ ) ... | left to right |
Finally, I find basic knowledge is important.
Once upon a time, I see on some document telling that "updating the host field of user record to % can enable user connect to the mysql database from any host", so I followed the guide,tried from other side and failed.
Today I finally found the reason:
You need exec reload to make the change take effect using "./mysqladmim -uroot -p<your password> reload"
So I can connect from other PC to the mysql Server.
Just trick, but very useful.