Wednesday, 24 December 2014

Google Cardboard

Interesting!!
You only need a cardboard and an Android phone, you could start to develop VR!

Ref: https://www.google.com/get/cardboard/get-cardboard.html

Wednesday, 5 November 2014

Skin Button



Yeah, I've thought about doing smart phone as a projector, to be a big projector, to show image, slides, video, document...
something like that.
BUT! I've never thought about doing it as a tiny projector!
Such a nice idea!

refer: http://dl.acm.org/citation.cfm?id=2647356

Thursday, 21 August 2014

[C++] Container


size add delete access
vector size() push_back() pop_back() [], back()
list size() push_back() pop_back() back()
queue size() push() pop() back()
dequeue size() push_back(),
push_front()
pop_front(),
pop_front()
[], back()
priority_queue size() push() pop() top()
set size() iterators iterators iterators
multiset size() iterators iterators iterators
map size() iterators iterators [], iterators
multimap size() iterators iterators iterators

Tuesday, 29 July 2014

[C++] Why we need new/delete in C++? Can't malloc/free do the same thing?

The difference between malloc/free and new/delete is malloc/free are standard library, and new/delete are operator.
#include <iostream>
#include <cstdlib>

using namespace std;

class Obj
{
public :
    Obj(void){ cout << "Constructor" << endl; }
    ~Obj(void){ cout << "Destructor" << endl; }
    void Initialize(void){ cout << "Initialization" << endl; }
    void Destroy(void){ cout << "Destroy" << endl; }
};

void UseMallocFree(void)
{
    Obj  *a = (Obj *)malloc(sizeof(Obj));
    a->Initialize();

    //…

    a->Destroy();
    free(a);

}

void UseNewDelete(void)
{
    Obj  *a = new Obj;

    //…

    delete a;
}

int main()
{
    cout << "UseMallocFree" << endl;
    UseMallocFree();
    cout << endl << "UseNewDelete" << endl;
    UseNewDelete();

    return 0;
}
UseMallocFree
Initialization
Destroy

UseNewDelete
Constructor
Destructor

Ref.: http://fanqiang.chinaunix.net/a4/b2/20020722/060200273_b.html

Monday, 28 July 2014

[C++] Constructor/Copy Constructor/Assignment Operator/Destructor

1) Both Copy Constructor and Assignment Operator are call by address, not call by value
#include <iostream>

using namespace std;

class Array {
    public:
        int *_array;
        int size;

        Array(int input):size(input)
        {
            _array = new int[size];
        }

        void Set(int i, int v)
        {
            _array[i] = v;
        }

        int Get(int i)
        {
            return _array[i];
        }

        ~Array()
        {
            delete [] _array;
        }
};

int main()
{
    Array a(5);
    Array b = a;

    a.Set(0, 10);
    a.Set(1, 20);
    a.Set(2, 30);
    a.Set(3, 40);
    a.Set(4, 50);

    cout << a.Get(0) << " " << a.Get(1) << " " << a.Get(2) << " " << a.Get(3) << " " << a.Get(4) << endl;
    cout << b.Get(0) << " " << b.Get(1) << " " << b.Get(2) << " " << b.Get(3) << " " << b.Get(4) << endl;
    cout << &a << " " << a._array << endl;
    cout << &b << " " << b._array << endl;

    return 0;
}
10 20 30 40 50
10 20 30 40 50
0x7fff61f44a90 0x1180010
0x7fff61f44aa0 0x1180010
*** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0000000001180010 ***

the problem caused in this program:
- memory leak in b
- it was copied by "b._array = a._array;", either modified in b or a will change the result
- double free

2) Initialization list
#include <iostream>

using namespace std;

class A {
    public:
        A()
        {
            cout << "A constructor" << endl;
        }

        A(const A& a)
        {
            cout << "A copy constructor" << endl;
        }

        A& operator=(const A& a)
        {
            cout << "A assignment Operator" << endl;
        }
};

class B {
    public:
        B(A &input)
        {
            cout << "B consturctor" << endl;
            m_a = input;
        }

    private:
        A m_a;
};

class C {
    public:
        C(A& input):m_a(input)
        {
            cout << "C constructor" << endl;
        }

    private:
        A m_a;
};

int main()
{
    cout << "===A===" << endl;
    A a;
    cout << "===B===" << endl;
    B b(a);
    cout << "===C===" << endl;
    C c(a);

    return 0;
}
===A===
A constructor
===B===
A constructor
B consturctor
A assignment Operator
===C===
A copy constructor
C constructor

3) Const variable can only be initialed in initialization list
#include <iostream>

using namespace std;

class A {
    public:
        A(int input) { a = input; }
        void show() { cout << a << endl; }

    private:
        const int a;
};

int main()
{
    A aa(5);
    aa.show();

    return 0;
}
test2.cpp: In constructor ‘A::A(int)’:
test2.cpp:7:9: error: uninitialized member ‘A::a’ with ‘const’ type ‘const int’ [-fpermissive]
test2.cpp:7:28: error: assignment of read-only member ‘A::a’
#include <iostream>

using namespace std;

class A {
    public:
        A(int input):a(input) { }
        void show() { cout << a << endl; }

    private:
        const int a;
};

int main()
{
    A aa(5);
    aa.show();

    return 0;
}
5

4) The serial of constructor and destructor
#include <iostream>

using namespace std;

class A {
    public:
        A()
        {
            cout << "A constructor" << endl;
        }

        ~A()
        {
            cout << "A destructor" << endl;
        }
};

class B {
    public:
        B()
        {
            cout << "B constructor" << endl;
        }

        ~B()
        {
            cout << "B destructor" << endl;
        }
};

class C {
    public:
        C()
        {
            cout << "C constructor" << endl;
        }

        ~C()
        {
            cout << "C destructor" << endl;
        }
};

class Aa : public A {
    public:
        Aa(int in1):y(in1)
        {
            cout << "Aa constructor" << endl;
        }

        ~Aa()
        {
            cout << "Aa destructor" << endl;
        }

    private:
        B b;
        int y;
        C c;
};

int main()
{
    Aa hi(5);

    return 0;
}
A constructor
B constructor
C constructor
Aa constructor
Aa destructor
C destructor
B destructor
A destructor

Saturday, 26 July 2014

[C++] The difference between class and struct

class X {
    int a; // X::a is private by default
};

struct S {
    int a; // S::a is public by default
};

[note]: the variable in union is also public by default.



Ref. Working Draft, Standard for Programming Language C++

Monday, 14 July 2014

Jeff Bezos delivers graduation speech at Princeton University




How will you use your gifts? What choices will you make?

Will inertia be your guide, or will you follow your passions?

Will you follow dogma, or will you be original?

Will you choose a life of ease, or a life of service and adventure?

Will you wilt under criticism, or will you follow your convictions?

Will you bluff it out when you're wrong, or you apologize?

Will you guard your heart against rejection, or will you act when you fall in love?

Will you play it safe, or will you be a little bit swashbuckling?

When it's tough, will you give up, or will you be relentless?

Will you be a cynic, or will you be a builder?

Will you be clever at the expense of others, or will you be kind?

Wednesday, 25 June 2014

Ethernet Switch


1) Switches are the next evolution of bridges and the operation they perform is still considered bridging. In very basic terms a switch is a high port-count bridge that is able to make decisions on a port-by-port basis.

2) A switch maintains a MAC table and only forwards frames to the appropriate port based on the destination MAC.

3) If the switch has not yet learned the destination MAC it will flood the frame. (I've read some data that says it'll use arp to know the MAC.)

Q: How to collect the MAC Table?
A: Each end-point is labeled with a MAC address starting with AF:AF:AF:AF:AF.  The ‘dynamic learning’ is done be recording the source MAC address of incoming frames.  While the destination MAC address had not yet been learned, the switch would be forced to flood the frame to all ports except the one it received.


Ref.:
http://en.wikipedia.org/wiki/Network_switch
http://www.definethecloud.net/data-center-101-local-area-network-switching/

Bridge



1) A bridge is a device that connects two or more local area networks, or two or more segments of the same network.

2) The original bridges were typically 2 or more ports (low port counts) and could separate MAC addresses using the table for those ports.

3) In the OSI model bridging acts in the first two layers, below the network layer.


Q: How to make a bridge table?
A:



Ref.:
http://en.wikipedia.org/wiki/Bridging_(networking)
http://www.definethecloud.net/data-center-101-local-area-network-switching/
http://technet.microsoft.com/en-us/library/cc700841.aspx

Tuesday, 24 June 2014

Hub




1) It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming.

2) A hub works at the physical layer (layer 1) of the OSI model

3) There's 2 kinds of hub, Passive & Active (which needs adapter & it'll repeat the signals)


Ref.:
http://en.wikipedia.org/wiki/Ethernet_hub
http://www.definethecloud.net/data-center-101-local-area-network-switching/

Internetworking


Device
PHY
Data Link
Network
Others

Repeater

Same

Same

Same

Same

Hub

Same

Same

Same

Same

Bridge

Same/!Same

Same/!Same

Same

Same

L2 Switch

Same/!Same

Same

Same

Same

Router

Same/!Same

Same/!Same

Same

Same

L3 Switch

Same/!Same

Same/!Same

Same

Same

Gateway

Same/!Same

Same/!Same

Same/!Same

Same/!Same

OSI Model
Data unitLayerFunction
Host
layers
Data7. ApplicationNetwork process to application
6. PresentationData representation, encryption and decryption, convert machine dependent data to machine independent data
5. SessionInterhost communication, managing sessions between applications
Segments4. TransportReliable delivery of packets between points on a network.
Media
layers
Packet/
Datagram
3. NetworkAddressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.
Bit/Frame2. Data linkA reliable direct point-to-point data connection.
Bit1. PhysicalA (not necessarily reliable) direct point-to-point data connection.


Ref.:
http://www.cs.nthu.edu.tw/~nfhuang/chap14.htm
http://en.wikipedia.org/wiki/OSI_model

Monday, 23 June 2014

[Motion Sensor] Google Gesture



How touching!
It gets in a different level from Kinect, Leap or Ring.
With the same purpose of self-driving car, considering for minority.

Saturday, 21 June 2014

Music as a Language



There's no bad ideas.
Just like what Victor Wooten said, "if you play C and C# right next to each other, it probably sounds like those notes clash"
"Wrong"
"Bad"
"but if you take the C up in octave, play the C# and C again"
"the sound became beautiful"
"how could the same 2 notes sounds bad, clash in one instance and beautiful in another?"
"take this to life, when we see something bad or awful or horrible in life, maybe we just viewing it in wrong octave"
Change your viewpoint, change your perspective, and there's no bad idea.

Steve Jobs' 2005 Stanford Commencement Address



I'm Steve Jobs fan.

Elon Musk USC Marshall Undergraduate Commencement Speech



1) Working super hard.
2) Attract great people.
3) Focus on signal over noise.
4) Don't just follow the trend.
5) Now is the time to get risks.

Friday, 20 June 2014

Rawlemon Spherical Solar Energy Generator


Rawlemon Spherical Solar Energy Generator

Really impressive!!!
To create fire w/ magnifying glass is what we learned from science class in elementary school.
Somehow, we all forgot to use this simple application.

Rawlemon Solar Devices is on INDIEGOGO.

Thursday, 19 June 2014

Pyro Board



which remind me the music w/ lightening in The Sorcerer's Apprentice


it must full of the burning smell...


Advanced version:

Ref.:
http://nigelstanford.com/Cymatics/

[Motion Sensor] Ring



I've used Kinect to develop a project.
In survey stage, we also consider Leap.
It seems that Ring is also be a good solution.

Nike Football - The Last Game



Playing it like a game, not a job!
And there's no greater danger than playing it safe.
Anyway, it energizes me.

Thursday, 29 May 2014

[MIT] Note 2 of Introduction to C and C++

18.01 Single Variable Calculus

Lecture 4 : Data Structures, Debugging



note: Structure Memory
ex.
#include <stdio.h>

int main()
{
    struct X
    {
        short s; 
        int i; 
        char c;
    };

    struct Y
    {
        int i;
        char c;
        short s;
    };

    struct Z
    {
        int   i;
        short s;
        char  c;
    };

    printf("%ld\n", sizeof(struct X));
    printf("%ld\n", sizeof(struct Y));
    printf("%ld\n", sizeof(struct Z));

    return 0;
}

12
8
8

Ref. http://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/

[MIT] Note 1 of Introduction to C and C++

MIT 6.S096 Introduction to C and C++

Lecture 1: Compilation Pipeline


Ref. http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-s096-introduction-to-c-and-c-january-iap-2013/

[MIT] Note 1 of Single Variable Calculus

MIT 18.01 Single Variable Calculus

Lecture 1: Compilation Pipeline



Ref. http://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/

Monday, 26 May 2014

Unlock Mechanism

It's a cool and creative security solution!
Cant wait to download and try~

Ref. http://www.airsig.com/

Thursday, 8 May 2014

[C++] Generic Programmin

1) Function templates
2) Class templates
- inherit:
a)


b)

c)

d)

Ref.: Practice on Programming course from Peking University

Monday, 28 April 2014

The Area of Triangle

1. Coordinates


△ABC
= ADEC - △ADB - △BEC
= 1/2(x1y2 + x2y3 + x3y1 - x2y1 - x3y2 - x1y3)


2. Heron's Formula
△= sqrt(s(s-a)(s-b)(s-c))
x = 1/2 (a+b+c)



Ref.:
http://en.wikipedia.org/wiki/Triangle
http://euler.tn.edu.tw/area.pdf


Wednesday, 23 April 2014

Systems of Linear Equation in 2 Variable

How many can systems of linear equation have?
1. 1 Solution
2. Infinite Solutions
3. No Solution


A) 
If (a1 / a2 != b1 / b2), it involves lines that intersect exactly 1 time.
-- Situation 1

B) 
If (a1 / a2 == b1 / b2 == c1 / c2), it's a same line.
-- Situation 2

C)
If (a1 / a2 == b1 / b2 != c1 / c2), lines are parallel.
-- Situation 3


[Cramer's Rule]


where  A_i  is the matrix formed by replacing the ith column of  A  by the column vector  b .

 




to solve:http://zerojudge.tw/ShowProblem?problemid=a410
Code:

Ref. http://en.wikipedia.org/wiki/Cramer%27s_rule

Quadratic Formula

The result of 
is


Tuesday, 22 April 2014

[C++] Pointers

Noted down the important concepts:
1. Reference Operator (&)
ex.
myvar = 25;  
foo = &myvar;
bar = myvar; 

2. Dereference Operator (*)
ex.
baz = *foo;

3. Pointers & Arrays
It collects so many ways to get address from an array and set value to an array.
#include <iostream>
using namespace std;

int main ()
{
  int numbers[5];
  int * p;

  p = numbers;
  *p = 10;

  p++;
  *p = 20;

  p = &numbers[2];
  *p = 30;

  p = numbers + 3;
  *p = 40;

  p = numbers;
  *(p+4) = 50;

  for (int n=0; n<5; n++)
    cout << numbers[n] << ", ";
  return 0;
Output:
10, 20, 30, 40, 50,

4. Pointers and Const
int x;
      int *       p1 = &x;  // non-const pointer to non-const int
const int *       p2 = &x;  // non-const pointer to const int
int const *       p3 = &x;  // also non-const pointer to const int
      int * const p4 = &x;  // const pointer to non-const int
const int * const p5 = &x;  // const pointer to const int 

5. Pointers to Pointers
char a;
char * b;
char ** c;

a = 'z';
b = &a;
c = &b;

6. Pointers and Functions
#include <iostream>
using namespace std;

int addition (int a, int b)
{ return (a+b); }

int subtraction (int a, int b)
{ return (a-b); }

int operation (int x, int y, int (*functocall)(int,int))
{
  int g;
  g = (*functocall)(x,y);
  return (g);
}

int main ()
{
  int m,n;
  int (*minus)(int,int) = subtraction;

  m = operation (7, 5, addition);
  n = operation (20, m, minus);
  cout << n;
  return 0;
}
Output:
8
Mostly, we use function point in sqort().

7. Arrow
Same description below:
(*p).foo;
p->foo;

Ref. http://www.cplusplus.com/doc/tutorial/pointers/

Friday, 18 April 2014

Sikuli

Sikuli is a picture-driven computing

Let's see the Demo:

Monday, 20 January 2014

Amazon Prime Air



30 min. delivery!
Reminds me the Pizza Hot Motto: 30 Minutes or Free.