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

J.K. Rowling Speaks at Harvard Commencement

It shows not only her knowledge but also her sense of humor!

Touch Board: Interactivity Everywhere

I like the ring bell part!

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

[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

The Cloud Interactive Lamp

Ref: http://www.richardclarkson.com/cloud/

[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

[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

[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++

Jeff Bezos delivers graduation speech at Princeton University

"It's harder to be kind than clever."

---

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?

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

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 unit	Layer	Function
Host layers	Data	7. Application	Network process to application
		6. Presentation	Data representation, encryption and decryption, convert machine dependent data to machine independent data
		5. Session	Interhost communication, managing sessions between applications
	Segments	4. Transport	Reliable delivery of packets between points on a network.
Media layers	Packet/ Datagram	3. Network	Addressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.
	Bit/Frame	2. Data link	A reliable direct point-to-point data connection.
	Bit	1. Physical	A (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

[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.

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.

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.

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.

[Standford] Note 1 of Algorithms: Design and Analysis, Part 1

I. INTRODUCTION

II. ASYMPTOTIC ANALYSIS

III. DIVIDE & CONQUER ALGORITHMS

Ref. https://www.coursera.org/course/algo

[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/

Unlock Mechanism

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

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

Robots transform into furniture

pretty cool, isn't it?

[C++] Generic Programmin

1) Function templates
2) Class templates

• inherit:
  a)
  

b)

c)

d)

Ref.: Practice on Programming course from Peking University

Google Self-Driving Car

Really impressive! It could not only improve road safety and help people who cannot drive.
 

[C++] Access Specifier

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

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  is the matrix formed by replacing the ith column of  by the column vector .

 

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

	/**********************************************************************************/
	/* Problem: a410 "解方程" from TYVJ */
	/* Language: C (552 Bytes) */
	/* Result: AC(0ms, 328KB) judge by this@ZeroJudge */
	/* Author: birdca at 2014-04-24 14:12:05 */
	/**********************************************************************************/
	#include <stdio.h>
	int main()
	{
	int a, b, c, d, e, f;
	while (scanf("%d %d %d %d %d %d", &a, &b, &c, &d, &e, &f) != EOF)
	{
	double tmp = a * e - b * d;
	if (tmp == 0)
	{
	if (c * e == b * f)
	printf("Too many\n");
	else
	printf("No answer\n");
	}
	else
	{
	printf("x=%.2lf\n", (double) (c * e - b * f) / tmp);
	printf("y=%.2lf\n", (double) (a * f - c * d) / tmp);
	}
	}
	return 0;
	}

view raw zerojudge_a410.c hosted with ❤ by GitHub

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

Quadratic Formula

The result of 

is

Ref. http://en.wikipedia.org/wiki/Quadratic_formula

[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/

Sikuli

Sikuli is a picture-driven computing

Let's see the Demo:

Google Night Walk

https://nightwalk.withgoogle.com/en/

Let's visit Marseille!

Circuit Scribe: Draw Circuits Instantly

Let's see the Demo:

Ref. https://www.kickstarter.com/projects/electroninks/circuit-scribe-draw-circuits-instantly

Portable Wireless Charger

ARK

Amazon Prime Air

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