Kalyan Chakravorty Blog

Drive Book Notes

2010-01-12T12:55:00.000-08:00

Drive by Daniel H Pink talks essentially about 3 things

A - Autonomous
M - Mastery
P - Progress

These three characteristics are primary motivators which drive us.

Copay and coinsurnace

2009-08-17T23:25:00.001-07:00

Why and what to read?

2009-06-06T10:52:00.000-07:00

Often times I pick up a book loose interest in it and leave it and it is on my to do list to finish the book. Have you ever faced such situation?

I have realized this plan works for me and I am sure it will be different for every individual

- Decide what you want to study
- Question yourself as to why are you studying
- After I read a chapter can I summarize the chapter in a few sentences.
- Can I write a good/bad review for this book.
- Use the book learning and APPLY

Intel Ad Is Amazing.

2009-05-30T00:24:00.000-07:00

Mac imaging software

2009-05-28T16:02:00.000-07:00

Casper

Trying new RSS reader

2009-05-23T11:54:00.000-07:00

Trying the new Newsgator (mamidi) to check the RSS thing now.

Combine two files line by line

2009-05-14T07:33:00.000-07:00

file1
-----
a
b
c

file2
-----
1
2
3

Output
------
a 1
b 2
c 3

Use this: paste -d"\0" file1 file2 > Output

From: Here

Home ownership woes?

2009-05-02T09:05:00.001-07:00

I am not in the market for hunting homes but thought it might be a good idea to check what the process is

First steps detailed here are pretty good

Home Ownership

Some highlights

Education

Credit History

Budget

Research

Pre approval

Your Priorties

The search

You are home

I think choosing the right people for the job is what matters. To start with I will focus on choosing the right Realtor.

I see that most of the realtors claim that they are not pushy and are not like car salesman. Why are car salesman looked so down upon? Can a car salesman not say that I am not like a Realtor.

Well from my perspective these are two different salesman in two different contexts, one is selling you something in the range of 20K to 30K (if you are buying cars like Camry , Accord, Corolla, Civic etc).

Realtor is trying to get you into a house you like worth close to 200K to 400K (shouldn't I just go to Redfin). So the Realtor cannot be pushy like a cars salesman since I would be uncomfortable since it is such a huge amount and will walk away from it. I am not an expert but I would choose these when selecting realtor

Experience

References

In all circumstances he should have your interest

How comfortable he is with comparable sales and running repeatedly

Choosing a realtor is almost like you started a small company and hiring your first employee, would you hire someone if he did not have your interest.

A lot of home ownership is dependent on whom you choose at the end of the day as he or she can be the deal breaker. I will not like a realtor recommending me something without doing his research and showing me the numbers (As said "numbers don't lie").

Oracle setting timestamp format and query

2009-04-23T17:52:00.000-07:00

alter session set NLS_DATE_FORMAT='DD-MM-YYYY HH24:MI:SS'

select * from table where date > to_date('2009-04-01','yyyy-mm-dd');

Problems with macbook

2009-04-11T10:47:00.000-07:00

I started having this problem with my macbook and apparently I am not the only one
MacBook Crack

How to run a process even when your session ends and exits

2009-04-11T10:35:00.000-07:00

Process :
-run process (from zshell)

-Ctrl-Z (to suspend)

-disown

-kill -CONT

WalkScore of a Place

2009-04-05T11:53:00.000-07:00

Get Walkscore of your place is a pretty handy tool to find out how accessible is your place to the nearby restaurants, gorceries, banks etc.

Write a binary stream (cannot output to a string)

2009-03-25T15:56:00.000-07:00

std::string s(record.data.buf(), record.data.size());
ofstream file1;
file1.open ("/tmp/kalyan",ios::binary);
file1.write(bytebuffer, size);
file1.close();

Poker Basics

2009-02-15T12:02:00.001-08:00

Frpm "pokerbasics.com"

Better terminal for Mac

2009-02-14T14:22:00.000-08:00

Iterm is pretty good if you are not happy with the mac osx built in terminal

Prefix and Postfix operators in C++?

2009-01-31T11:17:00.000-08:00

Thanks to stackoverflow "JProgrammer"

"Taking a leaf from Scott Meyers, More Effective c++ Item 6: Distinguish between prefix and postfix forms of increment and decrement operations.

The prefix version is always preferred over the postfix in regards to objects, especially in regards to iterators.

The reason for this if you look at the call pattern of the operators.

// Prefix
Integer& Integer::operator++()
{
*this += 1;
return *this;
}

// Postfix
const Integer Integer::operator++(int)
{
Integer oldValue = *this;
++(*this);
return oldValue;
}

Looking at this example it is easy to see how the prefix operator will always be more efficient than the postfix. Because of the need for a temporary object in the use of the postfix.

This is why when you see examples using iterators they always use the prefix version.

But as you point out for int's there is effectively no difference because of compiler optimisation that can take place.
"

XML Streaming

2009-01-21T16:49:00.003-08:00

// Creates a new reader (potentially recycled).
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLStreamReader reader = factory.createXMLStreamReader(inputStream);

while (reader.getEventType() != XMLStreamConstants.END_DOCUMENT) {
switch (reader.next()) {
case XMLStreamConstants.START_ELEMENT:
if (reader.getLocalName().equals("Time")) {
// Reads primitive types (int) attributes directly (no memory allocation).
time.hour = reader.getAttributeValue("hour").toInt();
time.minute = reader.getAttributeValue("minute").toInt();
time.second = reader.getAttributeValue("second").toInt();
}
...
break;
}
}

XML Streaming

2009-01-21T16:49:00.001-08:00

C# Book to Read

2009-01-19T20:37:00.000-08:00

.Net Framework guidelines

Setting up a multiple display with MAC and linux

2009-01-14T10:59:00.000-08:00

This is my personal preferences can change:

1. Run Synergy server on linux
http://synergy2.sourceforge.net/

2. Run synergyc client on mac
http://sourceforge.net/projects/synergykm

3. Edit .synergy.conf on your home directory

section: screens
linux desktop:
mac client:
end
section: links
mac client:
right = linux desktop
linux desktop:
left = mac client
end

4. On you mac terminal i do this
alias command="killall -c ssh; ssh -nf -L 24800:localhost:24800 -L 5917:localhost:5901 -L 5918:localhost:5902 linuxbox -- 'sleep 999999999'"

There could be a better method here

5. For connecting the macbook to another monitor use this
mini dvi to vga adapter
http://store.apple.com/us/product/M9320G/A

You might have to restart your mac book here.

Vola you are done.

Factory Method Pattern

2008-12-30T10:55:00.000-08:00

Factory Method Pattern

Container Summary Complexity from StrousStroup

2008-12-28T13:41:00.000-08:00

Vector

[] - const
List Operations - O(n)+
Iterators - Random

List

List operation - const
Front operations - const
Back operations - const
Iterators - Bi

Dequeue
[] - const
List operations - O(n)
Front operations - const
Back operations - const
Iterators - Ran

List operations include
- Insert
- erase
- clear

StrousStroup Container Design : Review

2008-12-27T18:54:00.000-08:00

Notes from Container Design Chapter in StrousStroup

- What is a container?
A Container is an object that holds other objects

- What is an iterator?
Iterator is a means of traversing objects in the container (Used to navigate containers)

- Important member of a Container for iterator
iterator begin() //points to the first element
const_iterator begin() const

iterator end() //points to one-past-last element
const_iterator end() const

reverse_iterator rbegin()
const_reverse_iterator ebegin() const;

reverse_iterator end()
const_reverse_iterator rend() const;

- Element access in a vector

reference operator[] (size_type n); //unchecked access

reference at (size_type n); //checked access

- Passing vectors

f1(vector &)
f2(const vector &)

vector v(1000);
f1(v) //pass reference

- reserve in vector allocates space in advance

- capacity() gives the current numbers of reserved memory slots

- size() gives the current number of elements

- Pointer cannot address a unit of memory smaller than a byte

- Link
Vector Code

Teenage Wasteland (The Who Actually from Baba O'reilly)

2008-12-25T12:19:00.000-08:00

C++ Abstract Base Classes

2008-12-24T19:08:00.000-08:00

#include "string"
#include "sstream"
using namespace std;

class AbstractStatic {

public:
static std::string constructKey(int a, int b) {

std::ostringstream ostr;

ostr «« a «« ":" «« b «« endl;
return ostr.str();
}
virtual std::string makekey(int a, int b) = 0;
virtual ~AbstractStatic();

};

class AbstractConcrete: public AbstractStatic
{
public:
std::string makeKey(int a, int b) {
std::ostringstream ostr;

ostr «« a «« "+" «« b «« endl;
return ostr.str();
}

};

void foo(AbstractStatic* a) {

cout «« "In function foo" «« endl;
}

int main(int argc, char* argv[]) {

AbstractStatic* as;
AbstractStatic as; //this is an erro and foo(as) is also an error
string a = AbstractConcrete::constructKey(1,2);
foo(as);
cout «« a «« endl;
return 0;
}

VNC Client for MAC

2008-12-24T11:43:00.000-08:00

Stumbled upon this sourceforge project for VNC Client for MAC

Chicken for VNC

STL MAP

2008-12-20T00:29:00.001-08:00

From deez.info

"

Let’s say you have two STL std::maps with identical types, and you want to copy all the elements from one to the other. The easiest way to do this is to use map::insert():

typedef std::map map_t;

map_t map1;
map_t map2;

// Copy all elements from map1 to map2
map2.insert(map1.begin(), map1.end());

Alternatively, you could use the STL std::copy algorithm:

// Copy all elements from map1 to map2.
std::copy(map1.begin(), map1.end(), std::inserter(map2, map2.begin()));

Both methods’ performance should be an amortized O(n) because they insert records in sorted order and use the hinting form of map::insert.

Note that because both methods ultimately call map::insert they will not overwrite a preexisting key’s associated value. In other words, if map1 has the value V1 associated with key K and map2 the value V2 associated with the same key K, V2 will remain in map2 after the copy operation.

Let’s say you want to perform the copy but have map1’s values overwrite map2’s for identical keys. The first way to solve this problem that entered my mind was to write my own OutputIterator which performs an overwriting assignment and pass it to std::copy. However, there’s a far simpler approach. You can copy map2’s values into map1, relying on the fact that map2’s values won’t overwrite map1’s, and then swap the results:

map1.insert(map2.begin(), map2.end());
map2.swap(map1);

Thanks, Sam, for helping me figure all this out.
"

New York Times Time Machine

2008-11-22T18:15:00.000-08:00

From

New York Times Machine

Interestingly good open source which is used:

a) JetS3T
b) iText
c) Java API for Image Processing

Books to read :)

2008-10-18T11:07:00.001-07:00

Someday will read these book ;)

- Creative Habit
- DownShifting
- What color is your parachute

Books to read :)

2008-10-18T11:07:00.000-07:00

Someday will read these book ;)

- Creative Habit
- DownShifting
-

Don't make me think

2008-10-05T10:07:00.000-07:00

Reading this book off late Don't Make me think , Will keep updating it with interesting things which I find

1. Sherlock holmes to Dr Watson (on earth revolving around sun)
"What the deuce is it for me? You say we go around the sun. If we went round the moon it would not make a pennyworth of difference to me or to my work"

2. Nothing important should be more than 2 clicks away.

3. Creating a site get rid of the question marks
- If you can create a button do that don't make it a link.
- Make pages self-evident

4. We dont read pages we just scan them
- How users read the web (www.useit.com)

5. We don't make optimal choices. We staisfice(Models of man:Social and Rational)
-How people make decisions
- We choose the first reasonable option.

6. We don't figure out how things work, we muddle through

7. If your audience is going to act like your're designing billboards then design great billboards.

8. Billboards design 101
- Create a clear visual hierarchy on each page
- Take advantage of conventions
- Break up page into clearly defined areas
- Make it obvious what is clickable
- Minimize noise
9. Three mindless unambigous clicks equlas one click that requires thought.
- Making choices mindless.

10. "Get rid of half the words on each page then get rid of half of what's left"
- Elemts of Style
- Eliminates instructions by making everything self explanatory

Java Timer and TimerTask

2008-08-29T00:43:00.000-07:00

From java2s.com

"import java.util.Timer;
import java.util.TimerTask;

class MyTimerTask extends TimerTask {
public void run() {
System.out.println("Timer task executed.");
}
}

public class MainClass {
public static void main(String args[]) {
MyTimerTask myTask = new MyTimerTask();
Timer myTimer = new Timer();

/*
* Set an initial delay of 1 second, then repeat every half second.
*/
myTimer.schedule(myTask, 1000, 500);

try {
Thread.sleep(5000);
} catch (InterruptedException exc) {
}

myTimer.cancel();
}
}"

Olympics Mania!

2008-08-23T14:12:00.000-07:00

Recently stumbled upon this article on USATF site

Performance and Responsibility

Key points which i really liked about this article

"The Olympics are about good timing, good luck, good preparation and good execution. All those things have to come together"

"Dropping a baton isn't bad luck, it's bad execution."

"When the men's marathon concludes on Sunday, we'll still be the World's #1 Team in terms of medal count. We can be a much better team. And we will be."

It's goals like these which can make things happen. I think perhaps the most disheartening part of olympics for me was looking at lolo jones crying after she lost, considering that she was winning all the way to hit the penultimate hurdle not sure whether to call that bad luck or bad preparation and I am almost sure it is bad luck.

Lucene and Solr

2008-08-15T15:18:00.000-07:00

Solr
Lucene

Matching Brace in eclipse

2008-08-04T13:54:00.001-07:00

Matching Brace in Eclipse

Google Protocol Buff and JSON

2008-07-29T13:46:00.000-07:00

Google Protocol Buff

JSON

Why Randy Paush is my hero

2008-07-26T12:55:00.000-07:00

Simple reason I watched his video and haven't seen anyone with such energy

What is your tax bracket?

2008-07-19T14:07:00.000-07:00

From
http://www.bargaineering.com/articles/2008-federal-income-tax-brackets-official-irs-figures.html

"
2008 Tax Brackets
Tax Single Married Filing Jointly
10% Not over $8,025 Not over $16,050
15% $8,025 - $32,550 $16,050 - $65,100
25% $32,550 - $78,850 $65,100 - $131,450
28% $78,850 - $164,550 $131,450 - $200,300
33% $164,550 - $357,700 $200,300 - $357,700
35% Over $357,700 Over $357,700
"

What is equity

2008-07-14T00:02:00.000-07:00

From financial-dictionary.com

"Equity is a term whose meaning depends very much on the context. In general, you can think of equity as ownership in any asset after all debts associated with that asset are paid off. For example, a car or house with no outstanding debt is considered the owner's equity since he or she can readily sell the items for cash. Stocks are equity because they represent ownership of a company, whereas bonds are classified as debt because they represent an obligation to pay and not ownership of assets."

Google Acquisitions

2008-07-06T11:41:00.000-07:00

Google Acquisitions

Inspirational Quote

2008-07-04T15:34:00.000-07:00

From Jack Welch

"Control your destiny or someone else will"

Deservingly true.

Amazing Quote :)

2008-07-04T11:54:00.000-07:00

This quote I stumbled upon

"When a man with experience meet a man with money, the man with money gets the experience and the man with experience gets the money"

Print XML without parsing

2008-06-25T07:01:00.000-07:00

use HTML::Entities;
print "PRE" encode_entities($xml) "/PRE"

What is Street Date?

2008-06-23T07:36:00.001-07:00

Taken from Wikipedia http://en.wikipedia.org/wiki/Street_date

"In business, a street date is the date a particular product is to be released for sale to the general public.

Typically, retailers receive shipments of stock prior to its street date release, so that the product can be placed on display shelves for store opening that day. Shipments come marked very clearly with a "do not sell before release date" label designating a street date mandated by the distributor. Shipments may sometimes arrive up to three weeks in advance.

Retail outlets can be severely punished by manufacturers for releasing a product even a day before the street date. If a retailer breaches the contract establishing a street date, the manufacturer may impose fines, may withdraw privileges to distribute future products from that manufacturer, and may file a lawsuit to enforce the contract. However, there is no documentation of a retail chain or store being fined or any action taken against them."

Rectangular word copy/paste/delete

2008-06-20T16:34:00.001-07:00

hold down the [Alt] key while you click and drag

ByteBuffer to String

2008-06-18T15:35:00.000-07:00

ByteBuffer bytebuff = ...;
byte[] bytearr = new byte[bytebuff.remaining()];
bytebuff.get(bytearray);
String s = new String(bytearray);

Firefox download day Jun 17th

2008-06-12T17:06:00.000-07:00

From firefox website the download day has been announced to June 17th

XML vs JSON

2008-06-11T16:28:00.000-07:00

I always thought XML was too verbose, although XML acts as a great plumbing agent.
People using data exchange cannot afford to use such verbose data methods to transfer a vast amount of data over the wire.

JSON seem to be the way to go. Need to get more educated on it. JSON

Cut Command in Unix

2008-06-11T12:41:00.000-07:00

Cut command in unix can make your life a lot easier.

Most important of them are

-d (delimiter) by which the fields are separated
-f (fields) fields which you want to get it printed.

E.g w | cut -d' ' -f 1

Create History with FireFox

2008-06-07T17:02:00.000-07:00

Help firefox create history , and you can be a part of it

FireFox WorldRecord

What is the availability of blogspot?

2008-06-06T20:45:00.000-07:00

I often find my site to be unavailable (no one mentions why was it down), i wonder blogspot availability is 95% :) seems to be a good number.

That is the price of using a free thingy would be :) ,

IPL final

2008-06-01T07:26:00.000-07:00

It is between Chennai vs Rajashtan!

No one expected :) this to be the case, I hardly watched all the matches :) but should to be able to buy one. Some free options from google search though not sure if they work

http://live-sports-streaming.blogspot.com/
http://picasa.tv

Gartner top 10

2008-05-31T00:04:00.001-07:00

from ehomeupgrade.com
Gartner’s top 10 disruptive technologies 2008-2012:

* Multicore and hybrid processors
* Virtualisation and fabric computing
* Social networks and social software
* Cloud computing and cloud/Web platforms
* Web mashups
* User Interface
* Ubiquitous computing
* Contextual computing
* Augmented reality
* Semantics

Java ByteBuffer

2008-05-28T17:37:00.000-07:00

from java.sun.com
Invariants

The following invariant holds for the mark, position, limit, and capacity values:

0 <= mark <= position <= limit <= capacity

A newly-created buffer always has a position of zero and a mark that is undefined. The initial limit may be zero, or it may be some other value that depends upon the type of the buffer and the manner in which it is constructed. The initial content of a buffer is, in general, undefined.
Clearing, flipping, and rewinding

In addition to methods for accessing the position, limit, and capacity values and for marking and resetting, this class also defines the following operations upon buffers:

*

clear() makes a buffer ready for a new sequence of channel-read or relative put operations: It sets the limit to the capacity and the position to zero.
*

flip() makes a buffer ready for a new sequence of channel-write or relative get operations: It sets the limit to the current position and then sets the position to zero.
*

rewind() makes a buffer ready for re-reading the data that it already contains: It leaves the limit unchanged and sets the position to zero.

Java Basics

2008-05-28T13:40:00.000-07:00

cretaeClassObject (String name)
{
Object retObj = null;
return(retObj = Class.forName(name).newInstance());
}

Java NIO

2008-05-27T10:26:00.000-07:00

http://exampledepot.com/egs/java.nio/pkg.html

http://java.sun.com/j2se/1.4.2/docs/api/java/nio/channels/Selector.html

http://www.cs.brown.edu/courses/cs161/papers/j-nio-ltr.pdf

Check if hash value is empty

2008-03-06T16:54:00.001-08:00

unless (%hash) {
hash is empty
}

Memory taken by a process

2008-02-27T12:49:00.000-08:00

watch -n 1 cat /proc/proc number/status

What is a freudian slip

2008-02-07T09:49:00.001-08:00

http://en.wikipedia.org/wiki/Freudian_slip

What greg wilson reads?

2007-12-08T00:15:00.000-08:00

I head greg when he was talking about beautiful code and hence then started to look at his blog

I find his reads to be pretty good
http://pyre.third-bit.com/blog/archives/1145.html
pasted from the link above
What I Read

A grad student mailed me this morning to ask me what I read to stay on top of things. In no particular order:

Journals

* ACM Computing Surveys
* ACM Queue
* ACM SIGCSE Bulletin
* ACM SIGSOFT Software Engineering Notes
* ACM Transactions on Software Engineering and Methodology
* Communications of the ACM
* IEEE Computer
* Computer Science Education
* Computing in Science & Engineering
* Empirical Software Engineering
* IEEE Software
* IEEE Transactions on Software Engineering
* Journal of Software Maintenance and Evolution
* SIGCSE: Technical Symposium on Computer Science Education
* Software: Practice and Experience

Blogs

* Adam Goucher
* Apress
* Artima
* Beautiful Code
* Blake Winton
* CBC | Toronto News
* CBC | World News
* Computer Science Community
* Consulting Toolsmiths - Matt Doar
* Cool Tools
* CTWatch Blog
* Daily Life in an Ivory Basement
* Daily Python-URL
* David Crow
* Diomidis D. Spinellis
* DrDobbs Portal Blog
* Google Code - Updates
* Google Summer of Code Blog
* Google Testing Blog
* Irving Reid
* Jazz Community Events
* Jazz Community News
* Joe Gregorio
* Joel on Software
* Jon Udell
* Lambda the Ultimate - Programming Languages Weblog
* Microsoft Research Publications
* O’Reilly Media, Inc. New Books
* O’Reilly Radar
* python-dev Summaries
* Safari Tech Books Online
* Schneier on Security
* ShowMeDo’s latest videos
* Strange Maps
* Streetknit
* The Tucows Blog
* Toronto Before: A Step Into The Past
* Upcoming.org: Events Search for
* Victor Ng
* Women in Technology
* xkcd.com

This entry was

7 Habits of innnovation

2007-11-20T09:29:00.001-08:00

fromt thinksimplenow.com
Have you ever looked at super creative or innovative people, and felt they are special beings blessed with gifts? Have you felt that you are not as fortunate? I used to feel this way. I have since learned that creativity is more about psychology than intellect, and there are no secrets to being creative. Actually, there is no such thing as “being more creative”, you are already a creative being.

I’m sure we can all relate to moments when we felt stuck trying to tap into our own creativity. Did you know that this block is merely your mind at work? Your mind is creating all sorts of assumptions, self-imposed constraints and self-limiting inhibitions. I have found that we can remove these assumptions just by being in the moment; start doing, and stop thinking.

Here are seven habits found in highly innovative and creative people that I’ve organized and summarized from Scott Berkun’s “the myths of innovation“.

1. Persistence - Innovation involves more than just great ideas. We need faith, hard work and a laser sharp focus for the end result to keep persisting for our vision in the face of roadblocks. We tend to see the end result of a creative idea in awe, but what we don’t see are the actions, hard work and persistence behind the scene to make the vision a reality.

“Invention is 1% inspiration, 99% perspiration“,
–Thomas A. Edison

2. Remove Self-Limiting Inhibitions - Under the spell of inhibition, we feel limited and stuck. We need to free ourselves from these mind-created constraints by removing assumptions and restrictions. This is what we refer to when we say “think outside the box”. Encourage ourselves to be open to new ideas and solutions without setting limiting beliefs. Remember, innovation is more about psychology than intellect.

3. Take Risks, Make Mistakes - I believe that part of the reason why we create self-imposed inhibition is due to our fear of failure. Expect that some ideas will fail in the process of learning. Build prototypes often, test them out on people, gather feedback, and make incremental changes. Rather than treating the mistakes as failures, think of them as experiments. “Experiment is the expected failure to deliberately learn something.” (Scott Berkun). Instead of punishing yourself for the failures, accept them, then take your newfound knowledge and put it towards finding the best solution. Live up to your goal of producing the best result, but understand you might hit roadblocks along the way.

“I have not failed. I’ve just found 10,000 ways that won’t work.”
–Thomas A. Edison

4. Escape - Our environment can and does effect how we feel. The more relaxed and calm we are internally, the more receptive we are to tap into our flowing creativity. This is why ideas sometimes come to us in the shower or while we’re alone. Each of us have different triggers to access our creative energy. I get into the ‘creative zone’ from sitting at my dining table, with a warm cup of chai, and my noise-canceling headphones. Many great thinkers go on long walks to help them solve problems. Experiment and find what works for you.

5. Writing Things Down - Many innovators and creative people keep a journal to jot down ideas and thoughts. Some keep a sketch book, scrap book, post-it notes, loose paper. They all have a method to capture their thoughts, to think on paper, to drop their inhibitions and start the creative process. Leonardo Da Vinci’s famous notebook was purchased by Bill Gates for $30.8 Million dollars.

6. Find Patterns & Create Combinations - Ideas come from other ideas. Did you know that Edison wasn’t the first one who came up with the invention of the light bulb? He was the first to build a workable carbon filament inside a glass bulb, that made light bulbs last longer. You can increase your exposure to new ideas, look for patterns and see how you can combine ideas to improve upon existing solutions.

7. Curiosity - Many innovators are just curious people who are inquisitive, and like to solve problems. Practice seeing things differently. For example, When seeing the solution to a problem, ask yourself, “What are some alternative ways to doing this?”. Ask a lot of questions and challenge the norms or existing methods.

Here are some techniques you can apply to cultivate creativity:

* Keep a Journal - Practice writing every thought, idea, and inspiration down. Practice, brainstorming and thinking on paper.
* Solve the Opposite Problem - Scott talked about this technique. The idea is to invent and brainstorm by solving the opposite problem that you are trying to solve. So, for example, if you are trying to create “The best laptop design”, then start with ideas to create “The worst laptop design”. For each idea you come up with, flip it. For example, if “heavy and clunky” is one idea for “The worst laptop design”, then flipping that might give me “light and sleek” which can be used in “The best laptop design”.
This technique works especially well when brainstorming in a group.The technique sounds so silly that people will become playful when answering. Humor brings down inhibition and encourages people to say things out aloud. People feel less insecure and more open.
* Find A Creative Environment - Find a relaxing or inspiring environment that triggers your creativity. Try different spots until you find some that really bring out the best in you. I alternate between my living room (which I have carefully decorated) and a couple of local coffee shops.
* Do something fun - If you’re stuck on something, shift your thoughts by going to do something fun and completely different. Come back to it with a fresh mind.
* Partnering - Find creative partnerships with another. New ideas can surface as a result of two forces that would not have been arrived by a single person. Brainstorm together.
* ‘Commit to Failure’ - “Commit yourself to taking enough risks that you will fail some of the time. If you’re not failing, we’re not doing something sufficiently difficult or creative.” -Scott Berkun
* Talk to Someone About It - I have found that when I try to articulate a particular problem to someone, that I’ll somehow articulate my solution, as well. When explaining my situation, I’m not expecting them to solve my problem, but rather act as a ‘bouncing board’ for ideas.
* **Plan for Roadblocks -Commit to efforts to overcome potential setbacks. It’s worthwhile to identify and have a plan for non-creative items that may inhibit creative thinking. Scott talked about the most common roadblocks people face: Loss of motivation, ran out of money, unable to convince key person.

C++ tricks from Jim Brooks

2007-11-18T23:06:00.000-08:00

C++ Programming Language

C++ Programming

Index

C++ Tricks

STL Code Snippets

Stream Code Snippets

Redirecting Streams

Overloaded Operators

Defining operator<<()

C++ Pitfalls & Traps

STL Pitfalls & Traps

C Preprocessor Tricks

Please click here if you notice any mistakes or have additions.

C++ Tricks



// To turn a fundamental type into a (somewhat) distinct type.
#define DECLARE_DISTINCT_TYPE( CLASS, T )                           \
class CLASS                                                         \
{                                                                   \
public:                                                             \
    CLASS( T val ) : mVal(val) { }                                  \
    operator T() const { return mVal; }                             \
    CLASS& operator=( const T& val ) { mVal = val; return *this; }  \
private:                                                            \
    T mVal;                                                         \
};
DECLARE_DISTINCT_TYPE( Radian, float )
DECLARE_DISTINCT_TYPE( Degree, float )
void Rotate( Radian rad );  // these overloaded functions become possible
void Rotate( Degree deg );  // yet can be manipulated as floats

STL Code Snippets



// Vector:
vector vec;
vec.push_back( name );      // push_back() means append
vec.clear();

// Iterating thru a container:
vector files;
vector::iterator itr;
for ( itr = files.begin(); itr != files.end(); ++itr )
    cout << *itr << endl;

// Iterating by subscript using an index (N/A to associative containers):
vector vec;
for ( int i = 0; i < vec.size(); ++i )

// Building and iterating thru a map and using pairs:
map mp;
mp.insert( pair( "a", 1 ) );
mp.insert( pair( "b", 2 ) );
mp.insert( pair( "c", 3 ) );
map::iterator itr;
for ( itr = mp.begin(); itr != mp.end(); ++itr )
    cout << itr->first << " " << itr->second << endl;

// To test if a key exists in a map/set:
if ( mMap.find(key) != mMap.end() )

// Adding then removing from a container.
list l;
for ( int i = 0; i < 10; ++i )
    l.push_back( i );  // append
while ( ! l.empty() )
{   // Prints/pops oldest (head) element first,
    cout << l.front() << endl;
    l.pop_front();
}

// If no match.
if ( map.find("key") == map.end() ) cout << "not found" << endl;

// Print a container.
list con;
copy( con.begin(), con.end(), ostream_iterator(cout," ") );

// Copy a container:
copy( con1.begin(), con1.end(),
      con2 );                // WRONG/PITFALL if con2 smaller than con1

con2.clear();
copy( con1.begin(), con1.end(),
      back_inserter(con2) ); // OK if con2 smaller than con1

// Sorting using a binary predicate:
// An alternative (using the container container pointers instead
// of values) that doesn't need a binary predicate is to define
// your own operator<() which sort() uses by default.
bool BinPred( const Class& o1, const Class& o2 )
{
    return o1.val < o2.val;
}
vector vec;
sort( vec.begin(), vec.end(), BinPred );

// A function that returns a pair.
// The pair is returned by value (like a struct would be, so it isn't dangling).
std::pair

AddMul( float x, float y )
{
    std::pair res;
    res.first  = x + y;
    res.second = x * y;
    return res;
}

// Print a binary number in base 2 using bitset.
#include 
bitset<8> val = 0xff;
cout << val;

// Turn string to all upper-case.
string s;
transform( s.begin(), s.end(),
           s.end(),
           toupper );

// Distance between two iterators.
distance( itr1, itr2 )

// Getting the iterator of an item that was inserted into a map:
// (a multimap/multiset differs, adapted from gfx_share.hh)
std::pair insertion;
insertion = mMap.insert( std::make_pair( *obj, std::make_pair(copy,1) ) );
itr = insertion.first;  // insertion is assumed to succeed (bool not checked)

// Replacing/substituting chars of a string.
// string::replace() is really an overwrite, not a substitution.
char
Unix2DosDirChar( char c )
{
    return c == '/' ? '\': c;
}
string
Unix2DosDir( const string& dirname )
{
    string s = dirname;
    std::transform( s.begin(), s.end(),
                    s.begin(),
                    Unix2DosDirChar );
    return s;
}

Stream Code Snippets



// Save/restore stream flags.
std::ios::fmtflags savedFlags = cout.flags();
...
cout.flags(savedFlags);

// showbase (eg automatically print "0x" prefix for hex, etc).
cout.setf( std::ios::showbase );

// Set float precision.
mStream.setf( ios::fixed, ios::floatfield );
mStream.precision( 20 );

// Writing to an integer to a stream using width/precision.
// Note that width/precision is discarded after every call to stream object!
std::cout << std::setw(5) << std::setfill('0') << x << ' ';
std::cout << std::setw(5) << std::setfill('0') << y << ' ';
std::cout << std::setw(5) << std::setfill('0') << z << ' ' << std::endl;

// Convert an int to a string stream for the purpose
// of passing the int as a C++ string.
int i;
ostringstream ss;
ss << i; Print( ss.str() );

// Open for reading to test if file is empty.
strm.open( fname, ios::in|ios::binary );
if ( strm.good() && strm.is_open() )
{
    // File exists.  Is it empty?
    strm.seekg(1);
    char c; strm >> c;  // a read is required to trigger EOF, seekg(1) alone won't
    if ( strm.eof() )
        cout << "File exists and is empty." << endl;
    else
        cout << "File exists and contains data." << endl;
}
else
{
    cout << "File doesn't exist." << endl;
}

// Reopen in R/W mode.
strm.close();
strm.clear();
strm.open( fname, ios::in|ios::out|ios::trunc|ios::binary );
strm.seekp(0);

Redirecting Streams

To write a class that redirects a stream to something else, define your own
streambuf class, then construct an ostream with pointer to the streambuf object.
An example is in Nicolais Josuttis's STL book.

A faux-pas is trying to derive from ostream (see prog/c++/streamRedirectionFauxPas.cc).
One problem is that passing endl will result in a "bad cast&qout; exception (g++ 3/4).

http://shekel.jct.ac.il/cc-res/online-doc/libgPP/iostream_28.html

http://www.lysator.liu.se/c/bs-errata-1.html

http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6

Defining operator<<()

The idea is to overload operator<<() with your user-defined type.



class Point
{
public:
    int x, y;
};

ostream&
operator<<( ostream& strm, const Point& obj )
{
    strm << "(" << obj.x << "," << obj.y << ")";
    return strm;
}

Overloaded Operators

Overloaded operators, except assignment, are inherited.
But subtle compiler errors can occur.

Let's say you have two related classes that are logically different types,
but are structurally equivalent (identical members).



class Vertex
{
public:
    Vertex& operator+( const Vertex& src );

    float x, y, z;
};

class WorldVertex : public Vertex
{
public:
};

Now try adding two derived objects:



void Draw( const WorldVertex& v );

WorldVertex v1, v2, v3;
v3 = v1 + v2;      // compile error
Draw( v1 + v2 );   // ok

Some compilers will give obscure errors, leading you to think
that you need to duplicate all the overloaded operator code
into every derived class. That wouldn't ideal.

What's happening in v3 = v1 + v2

is that Vertex::operator+() is called which returns a base Vertex object,
not a derived WorldVertex object.
You might think assigning a base object into a derived object is an immediate error.
But the C++ compiler first tries to find the matching assignment operator
such as Derived& operator=( const Base& ):



class WorldVertex : public Vertex
{
public:

    WorldVertex& operator=( const Vertex& src )
    {
        x = src.x;
        y = src.y;
        z = src.z;
        return *this;
    }
};

Because these classes are structurally equivalent,
Derived& operator=( const Base& ) does make sense,
as it can simply copy .x, .y, .z.

C++ Pitfalls & Traps

C++ has a zillion pitfalls, this lists some of the worst.

Reusing or abusing assignment operator=() in a copy constructor:

This pitfall exists with more complex classes whose members aren't fundamental types.
Assignment operators should free members before reassigning them.
If an operator=() that frees resources is called in a copy constructor,
it will try to free garbage. A solution is have separate Copy() and Free() methods.



class Class
{
public:
    Class( const Class& src )
    {
       *this = src;      // the temptation to write terse code leads to a pitfall
    }
    Class& operator=( const Class& src )
    {
        delete mObj;     // free members
        mObj = src.Obj;  // reassign members
        return *this;
    }
private:
    Class2*   mObj;
};

Method overriding will fail if you forget to write virtual
by a method in base class or the function signatures differ.

Calling a virtual method from a base constructor.

Think about the order of construction: the derived object hasn't been constructed yet.

Default copy constructors or assignment operators may cause trouble.

Safegaurds writing a dummy default copy constructor as private and/or with assert(0).

A constructor with a single arg might be misinterpreted as a conversion operator.

Use the keyword explicit if conversion isn't desired.


Class( int );
int n;
Class obj = n; // converts an int to a Class obj !!

Temporary objects and reference args


void Byref( int& x )
{
    ...
    x = y;
}
Byref( a + 2 );   // oops, result went nowhere into a temp

operator bool()

operator bool() is seductive for tersely testing if an object is valid:


class Data
{
public:
    operator bool() const { return mValid; }
private:
    string mData;
};

void Process( Data& data )
{
    // Valid data?
    if ( data )
    {
    }
}


if ( data0 == data1 ) return;


if ( bool(data0) == bool(data1) ) return;  // true == true

STL Pitfalls & Traps

end()


for ( itr = files.begin(); itr < files.end(); ++itr )  // WRONG
for ( itr = files.begin(); itr != files.end(); ++itr ) // ok

reserve() vs. resize()

resize() expands the container -- reserve() doesn't!

Incrementing iterators


while ( itr++ != files.end() ) // WRONG, itr incremented past end

Short destination containers

This could be a bug if vec2 is shorter than vec.

copy() won't extend the destination container.


  copy( vec.begin(), vec.end(),
        vec2.begin() );

One solution is: vec2.resize( vec1.size() ).

Another is to use an insert iterator (insertor):


  copy( vec.begin(), vec.end(),
        back_inserter(vec2) );

Catenating a string with a char


  char baseName[] = "myfile";
  string suffix = "txt";
  string fileName = baseName + '.' + suffix;   // WRONG

This is wrong because the compiler misinterprets this as C's way
of adding an integer to a pointer rather than as C++ string catenation.
That is, the compiler's intepretation is:


  string fileName = &baseName[ int('.') ] + suffix;

C Preprocessor Tricks

Macro to expand a unique name:


// Arcane indirect trick to give a variable a unique name.
// Subtlety: If written on the same line, UNIQUE_NAME() expands the same name.
#define UNIQUE_NAME__(NAME,LINE) NAME##LINE
#define UNIQUE_NAME_(NAME,LINE)  UNIQUE_NAME__(NAME,LINE)
#define UNIQUE_NAME(NAME)        UNIQUE_NAME_(NAME,__LINE__)


	home © 2007 Jim Brooks Last modified: Thu May 24 14:11:14 EDT 2007

keywords: C++ STL programming language, C++ STL resources, C++ tricks recipes, Standard Template Library, C++ common phrases expressions idioms, C++ code snippets, C++ pitfalls traps quirks caveats, programming tricks, GNU gcc g++,

What is embedded database

2007-11-15T18:01:00.000-08:00

from dbazine.com

Embedded Database Primer

by James F. Koopmann

Introduction

If you’re anything like me, staying on top of current trends within the field of database administration is highly challenging at times. We are continually bombarded with new trends and technology that we cannot normally afford to try. For quite awhile, I have wondered what embedded databases were all about. I think of embedded databases as something small and contained in my cellular phone or as maintaining some information within my automobile. But what is the embedded database world really like?

I decided to reduce my learning curve and develop a primer about embedded databases by interviewing a vendor with this expertise. I posed a few high-level questions to Steve Wampler, Director of Database Marketing, Birdstep Technology who has worked successfully with embedded databases for some time:

Q. What exactly defines an embedded database?

We define an embedded database as a software component that is part of the application, not a separate running application. Its operations are invoked by the application. Another way to look at it is that embedded databases are embedded within an application.

Q. Can you explain to the layman how a database is embedded within an application?

It is embedded either as in-line code or linked libraries. In either case, it's code that is executed only when invoked by the application.

Q. How long has the embedded database industry been around?

More than 20 years — one could argue that since the beginning of software, embedded databases have been in existence.

Q. What drives the new features introduced in the embedded industry?

This is vendor-dependent. What you are seeing today is an application view for development — meaning features are being developed to do certain application tasks.

Q. What is the fastest growing business use for embedded databases?

One of the hottest is automotive.

Q. Does the embedded database community compete with the larger RDBMS vendors and in what regards?

In some cases, yes. One needs to look at the database market as a continuum with the embedded on one end and the enterprise on the other. There is a point in the continuum where the embedded databases are competing with the enterprise databases. Typically, this is a case where the plethora of features in enterprise databases is more important than the cost, size, and performance. These last three factors are the key advantage of embedded database over enterprise database.

Q. How do embedded databases differ from the typical relational databases such as Oracle, DB2, and SQL Server?

These databases are big, expensive, and slow. They are general purpose because they must serve a wide range of applications and users. They tend to be separate running applications that are independent of the system application.

Q. What are the top three features or business solutions for embedded databases?

Performance, small size, and price.

Q. Are embedded databases relational?

Yes. There are databases that are hierarchical (network model, XML model) as well.

Q. What is the Network Data Model?

The relational database model establishes and maintains inter-record relationships through common data fields. The Network Database Model establishes inter-record relationships directly, through physical links between the related records, rather than through common data fields.

Q. What applications are better suited for embedded databases?

Application-specific systems that have no or limited human administration or interruption.

Q. What type of applications are not meant for embedded databases?

Large enterprise systems.

Q. Are there any instances where you have seen successful conversions from major RDBMS vendors to an embedded database system?

Usually in business automation systems where the database needs to handle large data, multiple users, but can't be too expensive and must be allowed to be redistributed by the developer.

Q. What are the administration duties for maintaining an embedded database environment?

These are minimal because the application is usually the administrator.

Q. What are the tuning opportunities of an embedded database? Is there much a DBA can do for such a small footprint?

It depends on the functionality of the database. In our case, tuning can come through cache management (performance), using SQL or Native API (performance), user-defined procedures and functions.

Q. How exactly do embedded databases speed time to delivery of applications and cut development costs?

Every software application manages data. In most cases, the data is managed in a flat file — and this is fine for these applications as long as they have a short life cycle and their data is stagnant. If the application is going to have a long life cycle and/or going to grow in its use, having a database management system is 100 times cheaper to buy than to build and in many years quicker to develop.

Q. How robust is the availability, reliability, and recoverability of embedded databases?

Very robust — because of their applications, this is a must.

Q. When I hear high performance for embedded databases I immediately think they surely cannot keep up with the “big boys” in relational databases. What can we expect as far as performance from an embedded database?

This is highly dependent on if the application is mostly reading, writing, updating, etc. Typically you can find order-of-magnitude better performance in embedded database.

Q. Are there any typical limits to the size of an embedded database such as data size, footprint, or instruction set?

No.

Conclusion

Embedded databases differ from typical databases such as DB2, Oracle, and SQL Server in that it is completely integrated into the application or hardware device in such a way that the end-user has very little knowledge, if any, of its existence. Users and administrators are not burdened with time-consuming installations or maintenance as the database is literally packaged with the application and should be self maintaining.

Embedded databases are meant to run on many different platforms with various programming interfaces. The nature of embedding databases’ instruction sets being linked specifically within and for a specific application gives them a small footprint. A reduced instruction set allows them to achieve performance that is hard to beat. Surely, you wouldn’t want to put an Oracle instance within your cellular phone, but I might in my automobile.

James F. Koopmann is dedicated to providing technical advantage and guidance to companies within information technology. Over the years, James has worked with a variety of database-centric software and tools vendors as strategist, architect, DBA, and performance expert. He is an accomplished author appearing regularly within printed publications across the Web, and speaking at local area User Groups as well as industry conferences. He may be reached at jkoopmann@pinehorse.com or www.pinehorse.com.

Interesting People

2007-11-08T10:24:00.000-08:00

I wish I could meet these fabulous people one day :)

http://en.wikipedia.org/wiki/Eliot_Spitzer
http://en.wikipedia.org/wiki/Shirley_Ann_Jackson
http://en.wikipedia.org/wiki/Padmasree_Warrior

Good Investment Books

2007-11-01T23:52:00.000-07:00

1. Intelligent Investor (Benjamin Graham)
http://www.amazon.com/Intelligent-Investor-Book-Practical-Counsel/dp/B0002X1JKU/ref=pd_bbs_sr_1/104-2886434-5656728?ie=UTF8&s=books&qid=1193986477&sr=8-1

Prompt for linux

2007-06-21T12:27:00.000-07:00

Hit upon the basics of linux shell, (will add more)

1. export PS1="[${LOGNAME}@$(hostname)] # "

Diff between only specified lines in unix

2007-05-16T10:30:00.002-07:00

diff < (sed ' line1,line2!d' file1) < (sed 'line1,line2 !d' file2)

Converting Numbers to Strings and Strings to Numbers in C++

2007-05-14T11:15:00.000-07:00

http://www.parashift.com/c++-faq-lite/misc-technical-issues.html

Managing C++ Objects

2007-03-24T09:43:00.000-07:00

http://billharlan.com/pub/papers/Managing_Cpp_Objects.html

Managing C++ Objects

Here are some guidelines I have found useful for writing C++ classes. There are many good books on the subject, but they have not been sufficient to keep me out of trouble. The first time I returned to writing C++ after a year of writing Java, I was appalled at how much my design was constrained by managing the lifetime of objects. When C++ classes share objects, then they must negotiate who owns the object. Garbage collection is not available, and smart pointers often fall short.
§ Simple constructors

If your preferred constructor takes arguments, then define a default constructor (no arguments) and make it protected. Derived classes will require this method.

Define protected initialization methods void init(...) with arguments, and call them from your preferred constructors. Each initialization method should set all member variables to a valid state, without relying on constructor initialization blocks. Use these initialization methods from your public copy constructor and assignment operator, if required.

Remove everything from constructor initialization blocks except the simplest constructor of a superclass (preferably a default constructor). Call protected superclass initialization methods from the subclass initialization methods. Make initialization methods non-virtual to avoid hiding by derived classes (since the name will always be init(...).)

All init(...) methods should first call the init() equivalent of a default constructor, to initialize all member pointers, perhaps to nulls. If your constructor fails and throws an exception, then the destructor can be called safely.

Your constructors will now be much more flexible and robust. Derived class constructors can manipulate their arguments before initializing the superclass. (Superclass constructors can only be called in initialization blocks.) Within a single class, you can share more initialization between alternative constructors. You need not worry about the order of initialization blocks.
§ Implement "The Big Three"

Always define a copy constructor and an assignment operator. Don't let anyone use the default implementations. If your class contains pointers to objects which your class does not plan to delete, then just make these two methods private, without an implementation. Do not implement versions that make shallow copies. You do not want a user to accidentally make copies on the stack if required to call a non-copy constructor or clone method instead. Making copies of objects should be a very deliberate step Conversion operators (single-argument constructors) can be dangerous for the same reason.

Define a virtual destructor unless you never want anyone to derive from your class. Define a protected non-virtual void dispose() method that deletes the object's resources, then call this method from your destructor. (This is the destructor equivalent of an init() method.) You can use this method in assignment operators, initialization, and derived classes.
§ No references as members

A class member should never be a reference, whether const or non-const. A member's object reference can only be set in the initialization block of a constructor. You will not be able to set a reference member in an initialization method. A reference permanently prevents your class from replacing the object dynamically.
§ Optional ownership

If a constructor or initialization method takes a non-const object as an argument, then you must decide whether this wrapper class will assume ownership of this object. The destructor of a Bridge or Decorator class might need to delete the contained object. Or maybe not. If you have any doubt, then the constructor should allow the user to choose.
§ No pointers as arguments

Pass all objects to class methods and constructors as references. There is absolutely no advantage to passing objects as pointers. This rule is equally valid whether the objects are const or not.

I've already recommended that all class members be saved as pointers. You can easily take the address of an argument reference (with an ampersand) and assign it to your member pointer. Some C++ programmers do not seem to realize that the address of a reference is the same as the address of the original object. So they pass pointers when they want to save the argument, and references when they do not. This is a poor form of documentation, based on a misunderstanding.

If an object is passed to a constructor or initialization method, the user can expect the class to hang onto it. If a method saves an object from an argument, choose an appropriate name, like setColor(Color&) or addInterpolator(Interpolator&).

The worst excuse for using a pointer as an argument is that you want to give it a default value of null (0). You still have to document what a null object is supposed to mean. Worse, the user may overlook that the argument exists or is optional. Declare a separate method that lacks the extra argument. The effort is negligible.
§ Returning objects

One can always return objects from class methods by reference, either const or non-const. A user can take the address of the reference, if necessary, to save the object. But there are no drawbacks to returning objects always as pointers. Consistency is preferable, and most API's return pointers.

If you return an object allocated on the heap (with a new), then be clear who has ownership of the object--your class, the recipient, or a third party.

Think about whether you are breaking encapsulation of member data in a way that will prevent modification later.

Never return a reference to a class member allocated on the stack in the header file. If your class replaces the value, then the user may be left with an invalid reference, even though your object still exists. (Other reasons: Your class will never be able to remove the object as a member. A user may manipulate the logic of your class in unexpected ways.)

A method should modify an object constructed by the user by accepting it as a non-const reference. Returning the same object would be redundant and confusing.
§ Clean header files

A header file ideally includes only the header file of super-classes or of standard C++ libraries. All other classes can be forward declared, like class ClassName; or template class ClassName;. Forward declarations will greatly simplify your "make" dependencies and speed your builds. Repairs will be easier.

Member variables that are saved by value require your header to include another header file. Consider allocating such members on the heap, even if you must delete them in the destructor. Save member objects by value only when the default constructor creates a lightweight object with a useful state.

If you have reasons to put your entire implementation in the header file, then of course you cannot take advantage of forward declarations.
§ Write more Java

When you get a chance, write more Java to free your mind of such distractions. Your C++ will improve.
§ Examples

See an illustration of some of these patterns in [ ../code/cpp_prototype ] .

Bill Harlan

1998

Revision: 1.21 2004/09/14 18:01:26 harlan Exp $

Return to parent directory.

Process start time in Unix

2007-01-11T15:12:00.000-08:00

To find the start time of a process in unix use

ps -fu

zgrep "tosearch" *.gx | tr ',' '\12' | grep "tosearch"

Thread Safe and Thread Aware

2007-01-10T23:04:00.000-08:00

From codeproject.com(http://www.codeproject.com/csharp/syncroot.asp)

Thread aware:

At any given time, at most one thread can be active on the object. The object is aware of the threads around it and protects itself from the threads by putting all the threads in a queue. Since there can be only a single thread active on the object at any given time, the object will always preserve its state. There will not be any synchronization problems.
Thread safe:

At a given time, multiple threads can be active on the object. The object knows how to deal with them. It has properly synchronized access to its shared resources. It can preserve its state data in this multi-threaded environment (i.e. it will not fall into intermediate and/or indeterminate states). It is safe to use this object in a multi-threaded environment.

Using an object that is neither thread-aware nor thread-safe may result in getting incorrect and random data and mysterious exceptions (due to trying to access the object when it is being used by a thread and is in an unstable, in-between state at the instant of access of the second thread).

Efficient VIM editing

2007-01-09T18:34:00.000-08:00

http://jmcpherson.org/editing.html

Good Hash Discussion

2006-12-04T17:45:00.001-08:00

http://burtleburtle.net/bob/hash/doobs.html

Timers in C#

2006-12-01T11:33:00.000-08:00

From msdn2.microsoft.com
private void CreateTimer()
{
System.Timers.Timer Timer1 = new System.Timers.Timer();
Timer1.Enabled = true;
Timer1.Interval = 5000;
Timer1.Elapsed +=
new System.Timers.ElapsedEventHandler(Timer1_Elapsed);
}

private void Timer1_Elapsed(object sender,
System.Timers.ElapsedEventArgs e)
{
System.Windows.Forms.MessageBox.Show("Elapsed!",
"Timer Event Raised!");
}

Berkeley DB

2006-11-28T11:20:00.000-08:00

From : http://pybsddb.sourceforge.net/ref/intro/terrain.html
1. Berkeley DB is an embedded database that supports fairly simple data access with a rich set of data management services

Data access in this context means
a) insert b)update c)search d)delete
Data management in this context means that
a)Concurrency b)Transactions c)Recovery

Unix Ports

2006-11-02T15:24:00.000-08:00

From Google groups

netstat -lp

It will tell you which task is listening on the port.

fuser -v -n tcp 32768

Will tell you which task is listening on the specified port and under
which account it's running.

IE6 duh?

2006-10-30T00:59:00.000-08:00

urns out, IE doesn't like the script tags if they are using element minimization. I got the page rendering just as I intended by changing the tag to look like this:

Doing some research, I came across this post in theList by Eric Vitiello which clarifies this more. Apparently the DTD declaration for the script tag says , and the XHTML specs says (under Appendix C. 3):

Given an empty instance of an element whose content model is not EMPTY (for example, an empty title or paragraph) do not use the minimized form (e.g. use

and not

).

So, I guess this isn't really a bug in IE. I'd think instead, that this is a bug in the DTD itself. The script tag doesn't have to contain #PCDATA (in fact, I consider it graceful if it doesn't), and forcing it is, well, stupid.

For now, I am explicitly closing the script tag with a seperate closing tag, and everything seems to be working well. Does anyone have any idea about handling this better, preferably with minimized element closures

stolen from piecesofrakesh.blogspot.com

When do you need a pointer to a reference?

2006-10-23T19:31:00.000-07:00

From C++ groups
> Why/when would someone need a pointer to a reference?

Never. A reference is another name for a real thing. A pointer can only
point to a real thing - it can't point to a name for a real thing.

References are often implemented as secret pointers, but it breaks the
language if you try to get a handle on this secret pointer - it is an
implementation detail.

If you meant a reference to a pointer, use this when you need something to
grab your pointer, point it to something else, and give the result back to
you. Consider a parser that reads statements written by the user:

WORD_TYPE getWord (char *&statement);

Each time you call this function it finds a word, returns its type, and
points the pointer off the end of the word.

VIM split

2006-10-20T00:42:00.000-07:00

Vim viewport keybinding quick reference

:sp will split the Vim window horizontally. Can be written out entirely as :split .

:vsp will split the Vim window vertically. Can be written out as :vsplit .

Ctrl-w Ctrl-w moves between Vim viewports.

Ctrl-w j moves one viewport down.

Ctrl-w k moves one viewport up.

Ctrl-w h moves one viewport to the left.

Ctrl-w l moves one viewport to the right.

Ctrl-w = tells Vim to resize viewports to be of equal size.

Ctrl-w - reduce active viewport by one line.

Ctrl-w + increase active viewport by one line.

Ctrl-w q will close the active window.

Ctrl-w r will rotate windows to the right.

Ctrl-w R will rotate windows to the left.

From Linux.com

Javascript :quirkmodes.org

2006-10-19T14:52:00.000-07:00

http://www.quirkmodes.org

CRON

2006-09-25T10:26:00.000-07:00

minute hour dom month dow user cmd

minute This controls what minute of the hour the command will run on,
and is between '0' and '59'
hour This controls what hour the command will run on, and is specified in
the 24 hour clock, values must be between 0 and 23 (0 is midnight)
dom This is the Day of Month, that you want the command run on, e.g. to
run a command on the 19th of each month, the dom would be 19.
month This is the month a specified command will run on, it may be specified
numerically (0-12), or as the name of the month (e.g. May)
dow This is the Day of Week that you want a command to be run on, it can
also be numeric (0-7) or as the name of the day (e.g. sun).
user This is the user who runs the command.
cmd This is the command that you want run. This field may contain
multiple words or spaces.

AJAX the Diagram

2006-09-21T18:21:00.000-07:00

http://www.adaptivepath.com/images/publications/essays/ajax-fig1.png

STL:Map

2006-08-21T16:04:00.000-07:00

from metashell.com
#pragma warning(disable: 4786)

#include
#include
#include

using namespace std;

int main() {
map ass_array;

// Assign keys and values

ass_array["fat"] = 0;
ass_array["sodium"] = 45;
ass_array["totalcarb"] = 46;
ass_array["protien"] = 0;

// Insert Value

ass_array.insert( map::value_type( "potassium", 25 ) );

// Print value of sodium

cout << ass_array["sodium"] << endl;
cout << "The map has " << ass_array.size() << " entries.\n";

// Iterator used to hold position in the map

map::iterator loc;

// Returns same value as ass_array.end() if not find.

loc = ass_array.find("sugar");

if(loc != ass_array.end())
cout << "Sugar found!\n";
else
cout << "No Sugar\n";

return 0;
}

STL:Sort

2006-08-21T12:32:00.000-07:00

From msoe.edu

#include
#include // Include algorithms
using namespace std;

vector vec;
vec.push_back (10);
vec.push_back (3);
vec.push_back (7);

sort(vec.begin(), vec.end()); // Sort the vector

// The vector now contains: 3, 7, 10

STL: find

2006-08-21T12:31:00.000-07:00

list nums;
list::iterator nums_iter;

nums.push_back (3);
nums.push_back (7);
nums.push_front (10);

nums_iter = find(nums.begin(), nums.end(), 3); // Search the list.
if (nums_iter != nums.end())
{
cout << "Number " << (*nums_iter) << " found." << endl; // 3
}
else
{
cout << "Number not found." << endl;
}

Sharing mouse and keyboard between two computers with different operating system

2006-08-15T14:39:00.000-07:00

from http://synergy2.sourceforge.net

Running Synergy

Synergy lets you use one keyboard and mouse across multiple computers. To do so it requires that all the computers are connected to each other via TCP/IP networking. Most systems come with this installed.

Step 1 - Choose a server

The first step is to pick which keyboard and mouse you want to share. The computer with that keyboard and mouse is called the "primary screen" and it runs the synergy server. All of the other computers are "secondary screens" and run the synergy client.

Step 2 - Install the software

Second, you install the software. Choose the appropriate package and install it. For example, on Windows you would run SynergyInstaller. You must install the software on all the computers that will share the mouse and keyboard (clients and server). On OS X you'll just have a folder with some documentation and two programs. You can put this folder anywhere.

Step 3 - Configure and start the server

Next you configure the server. You'll tell synergy the name of the primary and secondary screens, which screens are next to which, and choose desired options. On Windows there's a dialog box for setting the configuration. On other systems you'll create a simple text file.

Note that when you tell synergy that screen A is to the left of screen B this does not imply that B is to the right of A. You must explicitly indicate both relations. If you don't do both then when you're running synergy you'll find you're unable to leave one of the screens.

Windows
On Windows run synergy by double clicking on the synergy file. This brings up a dialog. Configure the server:

* Click the Share this computer's keyboard and mouse (server) radio button
* Click the Screens & Links Configure... button
* Click the + button to add the server to the Screens list
o Enter the name of server (the computer's name is the recommended name)
o Optionally enter other names the server is known by
o Click OK
* Use the + button to add your other computers
o Using a computer's name as its screen name is recommended
o Choose desired screen options on the Add Screen dialog
* Use the controls under Links to link screens together
o Click (once) on the server's name in the Screens list
o Choose the screen to the left of the server; use --- if there is no screen to the left of the server
o Choose the screens to the right, above and below the server
o Repeat the above steps for all the other screens
* Click OK to close the Screens & Links dialog
* Use Options... to set desired options
* If the server's screen name is not the server's computer name:
o Click Advanced...
o Enter the server's screen name next to Screen Name
o Click OK

Now click Test. The server will start and you'll see a console window with log messages telling you about synergy's progress. If an error occurs you'll get one or more dialog boxes telling you what the errors are; read the errors to determine the problem then correct them and try Test again. See Step 5 for typical errors.

Unix or Mac OS X
Create a text file named synergy.conf with the following:

section: screens
screen1:
screen2:
end
section: links
screen1:
right = screen2
screen2:
left = screen1
end

Replace each occurrence of screen1 with the host name of the primary screen computer (as reported by the hostname program) and screen2 with the host name of a secondary screen computer. In the above example, screen2 is to the right of screen1 and screen1 is to the left of screen2. If necessary you should replace right and left with left, right, up, or down. If you have more than two computers you can add those too: add each computer's host name in the screens section and add the appropriate links. See the configuration guide for more configuration possibilities.

Now start the server. Normally synergy wants to run "in the background." It detaches from the terminal and doesn't have a visible window, effectively disappearing from view. Until you're sure your configuration works, you should start synergy "in the foreground" using the -f command line option.

On unix type the command below in a shell. If synergys is not in your PATH then use the full pathname.

synergys -f --config synergy.conf

On OS X open Terminal in the Utilities folder in the Applications folder. Drag the synergys program from the synergy folder onto the Terminal window. The path to the synergys program will appear. Add the following to the same line, type a space at the end of the line but don't press enter:

-f --config

Now drag the synergy.conf file onto the Terminal window and press enter. Check the reported messages for errors. Use ctrl+c to stop synergy if it didn't stop automatically, correct any problems, and start it again.

Step 4 - Start the clients

Next you start the client on each computer that will share the server's keyboard and mouse.

Windows
On Windows run synergy by double clicking on the synergy file. This brings up a dialog. Configure the client:

* Click the Use another computer's shared keyboard and mouse (client) radio button
* Enter the server's computer name next to Other Computer's Host Name
o This is not the server's screen name, unless you made that the server's host name as recommended
* If the client's screen name is not the client's computer name:
o Click Advanced...
o Enter the client's screen name next to Screen Name
o Click OK

Now click Test.

Unix or Mac OS X
To start a client on unix, enter the following:

synergyc -f server-host-name

where server-host-name is replaced by the host name of the computer running the synergy server. If synergyc is not in your PATH then use the full pathname.

On OS X open Terminal in the Utilities folder in the Applications folder. Drag the synergyc program from the synergy folder onto the Terminal window. The path to the synergys program will appear. Add the following to the same line and press enter:

-f server-host-name

When you added the client to the server's configuration you chose a name for the client. If that name was not client's host name then you must tell the client the name you used. Instead of the above command use this instead:

synergyc -f --name name server-host-name

where name is the name for the client in the server's configuration. (On OS X drag the synergyc program to the Terminal window rather than typing synergyc.)

Step 5 - Test

Clients should immediately report a successful connection or one or more error messages. Some typical problems and possible solutions are below. See the troubleshooting and the FAQ pages for more help.

* failed to open screen (X11 only)

Check permission to open the X display;
check that the DISPLAY environment variable is set
use the --display command line option.

* address already in use

Another program (maybe another copy of synergy) is using the synergy port; stop the other program or choose a different port in the Advanced... dialog. If you change the port you must make the same change on all of the clients, too.

* connection forcefully rejected

The synergy client successfully contacted the server but synergy wasn't running or it's running on a different port. You may also see this if there's a firewall blocking the host or port. Make sure synergy is running on the server and check for a firewall.

* already connected

Check that the synergy client isn't already running.

* refused client

Add the client to the server's configuration file.

* connection timed out

Check that server-host-name is correct.
Check that you don't have a firewall blocking the server or synergy port.

* connection failed

Check that server-host-name is correct.

If you get the error "Xlib: No protocol specified" you're probably running synergy as root while logged in as another user. X11 may prevent this for security reasons. Either run synergy as the same user that's logged in or (not recommended) use "xhost +" to allow anyone to connect to the display.

When successful you should be able to move the mouse off the appropriate edges of your server's screen and have it appear on a client screen. Try to move the mouse to each screen and check all the configured links. Check the mouse buttons and wheel and try the keyboard on each client. You can also cut-and-paste text, HTML, and images across computers (HTML and images are not supported on OS X yet).

Step 6 - Run

Once everything works correctly, stop all the clients then the server. Then start the server with the Start button on Windows and without the -f option on Unix and Mac OS X. Finally start the clients similarly. On Windows before clicking Start you may want to set the Logging Level to Warning so the logging window doesn't pop up (because you currently can't close it, just minimize it).

You can also configure synergy to start automatically when your computer starts or when you log in. See the autostart guide for more information.

Command Line Options Guide

Common Command Line Options
The following options are supported by synergys and synergyc.
-d, --debug level use debugging level level
--daemon run as a daemon (Unix) or background (Windows)
-f, --no-daemon run in the foreground
--display display connect to X server at display (X11 only)
-n, --name name use name instead of the hostname
--restart automatically restart on failures
-1, --no-restart do not restart on failure
-h, --help print help and exit
--version print version information and exit

Debug levels are from highest to lowest: FATAL, ERROR, WARNING, NOTE, INFO, DEBUG, DEBUG1, and DEBUG2. Only messages at or above the given level are logged. Messages are logged to a terminal window when running in the foreground. Unix logs messages to syslog when running as a daemon. The Windows NT family logs messages to the event log when running as a service. The Windows 95 family shows FATAL log messages in a message box and others in a terminal window when running as a service.

The --name option lets the client or server use a name other than its hostname for its screen. This name is used when checking the configuration.

Neither the client nor server will automatically restart if an error occurs that is sure to happen every time. For example, the server will exit immediately if it can't find itself in the configuration. On X11 both the client and server will also terminate if the connection to the X server is lost (usually because it died).

Server Command Line Options

synergys [options]

The server accepts the common options and:

-a, --address address listen for connections on address address
-c, --config pathname read configuration from pathname

address has one of the following forms:

hostname
:port
hostname:port

hostname is a hostname or IP address of a network interface on the server system (e.g. somehost or 192.168.1.100). port is a port number from 1 to 65535. hostname defaults to the system's hostname and port defaults to 24800.

Client Command Line Options

synergyc [options] address[:port]

address is the hostname or IP address of the server and port is the optional netw

Explicit in C++

2006-08-14T10:07:00.000-07:00

Using Explicit in C++

In C++ it is possible to declare constructors for a class, taking a single parameter, and use those constructors for doing type conversion. For example:

class A {
public:
A(int);
};

void f(A) {}

void g()
{
A a1 = 37;

A a2 = A(47);

A a3(57);

a1 = 67;

f(77);
}

A declaration like:

A a1 = 37;

says to call the A(int) constructor to create an A object from the integer value. Such a constructor is called a "converting constructor".

However, this type of implicit conversion can be confusing, and there is a way of disabling it, using a new keyword "explicit" in the constructor declaration:

class A {
public:
explicit A(int);
};

void f(A) {}

void g()
{
A a1 = 37; // illegal

A a2 = A(47); // OK

A a3(57); // OK

a1 = 67; // illegal

f(77); // illegal
}

Using the explicit keyword, a constructor is declared to be
"nonconverting", and explicit constructor syntax is required:

class A {
public:
explicit A(int);
};

void f(A) {}

void g()
{
A a1 = A(37);

A a2 = A(47);

A a3(57);

a1 = A(67);

f(A(77));
}

Note that an expression such as:

A(47)

is closely related to function-style casts supported by C++. For example:

double d = 12.34;

int i = int(d);

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5 PHP Design Patterns

2006-07-25T11:21:00.000-07:00

Five common PHP design patterns
http://www-128.ibm.com/developerworks/library/os-php-designptrns/?ca=dnw-725

Writing your own newsreader

2006-07-18T22:49:00.000-07:00

From:www.indicthreads.com
XML feeds are the way today to keep a tab on what's happening in the blogosphere as well as to know about site updates and new additions. I had heard about two popular open source feature-rich Java APIs to deal with the feeds, ROME and Informa but could never really savor them.

For one of my own sites where I, sort of hand-built the aggregator as Myjavaserevr does not allow deploying external JARs or Taglibs I did not get any chance to play with these APIs. So when I got some opportunity it was imperative that I tried them.

The following is a very elementary example of using the two news aggregation libraries that imitates a newsreader. The examples, as I said, are pretty basic and they would make a hit to the specified Feed URL every time you call the JSPs. The code snippets are not meant to demonstrate good coding practice.

Both the libraries support almost all versions of RSS, RDF and Atom and features such as dynamic discovery of feed format. Feature wise probably Informa has an upper hand (it supports OPML, recognizes the Enclosure element making it suitable to comprehend Podcast feeds and can be configured to use a persistence mechanism built over Hibernate) but what it lacks is availability of documents. There are no primers at the site and the code is very poorly commented making the Javadocs difficult to come to pace quickly. The two Java.net articles that I could, Google have been outdated, as I used the 0.6.5 version of the library.

ROME, on the other hand, has very nice documentation available at its site, complete with code examples. Many desirable features are unfortunately still on the TODO list. For comprehending the "Enclosure" element ROME needs a separate plugin module (that also supports iTunes extensions). While I have not investigated them, there are a number of sub-projects based on both ROME and Informa, for example: there is a JSP Tag library based on Informa. There is a short review of various libraries here but I guess much stuff on Informa is not relevant now since its latest release.

I am not mincing my words when I say that each API has its own strengths, Informa library is pretty bulky but supports OPML while Rome has a wider support for all kind of XML feeds and has a pluggable architecture. The good thing about these APIs is that they pretty much offer you everything that you may want to do with feeds, reading, generating your own, and creating a digest from multiple feeds and so on.

To run these JSPs, needless to say, you would need to download Informa and ROME libraries. I ran these on jakarta-tomcat-5.0.28 / j2sdk1.4.2_06 and the only dependency I was missing was the JDOM jar that ROME needs.

Concurrent Prograaming Good Reference

2006-07-18T08:12:00.000-07:00

Concept and Notations in Concurrent Programming By Andrews and Schneider

Attribute Types

2006-07-17T11:06:00.000-07:00

from umn site

Distance Measures

2006-07-15T22:36:00.000-07:00

Concept Drift

2006-07-09T19:17:00.000-07:00

http://www.bloglines.com/blog/Tilmann?id=6

Concept Drift

2006-07-09T19:16:00.000-07:00

http://www.bloglines.com/blog/Tilmann?id=6

On the Business Delegate Pattern

2006-07-09T08:13:00.000-07:00

http://www-128.ibm.com/developerworks/java/library/j-ejb1022.html

J2EE pattern langugae

2006-07-09T08:02:00.000-07:00

from java.sun.com

What is business logic?

2006-07-04T10:35:00.000-07:00

The part of an application program that performs the required data processing of the business. It refers to the routines that perform the data entry, update, query and report processing, and more specifically to the processing that takes place behind the scenes rather than the presentation logic required to display the data on the screen (GUI processing). Client applications are made up of a user interface and business logic. Server applications are mostly business logic.

Both client and server applications also require communications links, but the network infrastructure, like the user interface, is not part of the business logic

Design Patterns: Visual

2006-07-04T08:59:00.000-07:00

Berkeley DB: Part Three

2006-06-26T07:35:00.000-07:00

Message Handler

package db.GettingStarted;
import com.sleepycat.db.Environment;
import com.sleepycat.db.MessageHandler;

public class MyMessageHandler implements MessageHandler
{
// Our constructor does nothing
public MyMessageHandler() {}
public void message(Environment dbenv, String message)
{
// Put your special message handling code here
}
}

Set the databaseconfig to use this messagehandler
package db.GettingStarted;
import com.sleepycat.db.DatabaseConfig;
...
DatabaseConfig myDbConfig = new DatabaseConfig();
MyMessageHandler mmh = new MyMessageHandler();
myDbConfig.setMessageHandler(mmh);

Chimney Bluff State Park

2006-06-26T07:34:00.000-07:00

http://www.fotosearch.com/CRT369/15420-01ns/

Visited this on 06/25/06