Take a bite off the elixir

I always get this question: Why a mac? Why pay so much for that piece of gadget (or contraption as most feel it is)?

Now I think it's high time I etched down the answer to that.

Firstly, I admit, it's almost impossible to convey certain emotions. (No kidding) You need to experience it to really understand that. Similar is my state with a mac. So, I'll try my best at it.

Before I even start, shall we clear the fog surrounding some 'Apple' 'terms'?

Mac: The hardware and software both are called Mac. There are a myriad of hardware designed and manufactured by Apple. Let me just list the computers.

      iMac: A desktop computer with your CPU tower built into the monitor itself. 

      Mac Mini: A BYODKM computer. Display, Keyboard,  Mouse separate.

      MacBook: A notebook (laptop)

      MacBook Pro: Notebook with extra cost ;-), extra cosmetic value, extra power
      (nowadays macbooks are equally powerful)
      Mac Pro: A BYODKM computer again but a very high end machine, with a form factor like the
      usual CPU towers we get and very costly too.

OS X: Jargon for mac OS version 10 which is the latest series of the OS

1. Version 10.0: Cheetah
2. Version 10.1: Puma
3. Version 10.2: Jaguar
4. Version 10.3: Panther
5. Version 10.4: Tiger
6. Version 10.5: Leopard
7. Version 10.6: Snow Leopard ( The lastest as of Jul 24, 2010 )

PC: Apple Inc. has chosen to call the computers running windows as PCs and their products as Mac. But in common terms, you can always call any computer you use at home or office (if you alone use it) a Personal Computer :-). Blame Apple for that!

With that done, let me start with myth-breaking...

A mac is difficult to use. It's for the geeks.

      Never. It can be used by anyone. Anyone who thinks can use a PC can use a mac. But yes, designers and developers use more of mac. That's because Mac is a blend of power and elegance. Power for geeks and elegance for noobs.

There isn't lotta software that is compatible with mac
      That was true when Apple stuck to its in-house PPC processors. Now that they are using Intel's Processors, times have changed. Almost any software you run on a PC (grrr. See that's how Apple's vocabulary infects you. Results from prolonged Mac usage) err..., Windows machine has a Mac counterpart. Most times, a better alternative is available on a mac.

A Mac can't run Windows

     Similar the previous myth. Now you can either run it natively like on a PC ( Forgive me. Honestly, it's difficult to adapt to this new vocab. Hence, PC = Windows machine in this post). or on a Virtual Machine like VMWare. Dual boot is very simple too. You can have both OS with no restriction. Apple gives you all required drivers too. Although I'll bet, you wont use windows once you use a Mac. 

A mac is costly
      That's INITIALLY true. It IS costly compared to other hardware that's available in the market. But believe me, it's WORTH IT. For the performance, the productivity, the life style, the peace of mind you get, YOU CAN PAY IT, actually more too. That's the thing that helps Apple have the nerve to price it so high. People fall in love with the mac. It's not everyday you buy a computer, is it?

If you ask a mac user a question: One mac or 4 PCs? What do you want?
An easy to guess answer: ONE MAC!!!

Now some personal advantages from my vantage point:

1. No crashes: Yeah. No crashes. It just works!!! Of course nothing is perfect. Software on macs crash too. But not even once in a blue moon. Even more rarely. 'Crash' is off your dictionary => No every- month-format-and-OS-reinstall.

2. No Viruses: Since, Mac OS under the hood runs over a flavor of Unix, (For more info, read abt Darwin) windows viruses are petrified in it.

3. Stable everything: Since the hardware and software are from Apple, it's the perfect marriage. So no incompatibilities. Almost all external hardware available in the market - printers, etc work well too.

4. Developer's haven: For software people like me, it's like having a Linux installation inside my everyday OS. I don't need a separate installation of Linux. You have the BASH and everything a developer needs already in here. Apache server, PHP, SNMP daemon etc. are already in there. For other tools, you can CONFIGURE, MAKE AND MAKE INSTALL from sources! Now you know why almost almost all conference videos have glowing Mac logos on the podium. Google geeks love Macs too.

Buying a mac was one of the best choices of my life. Actually, I wouldn't hesitate to say, if you are intelligent, YOU WOULD BUY A MAC.

யாம் பெற்ற இன்பம் பெருக இவ்வையகம்!

No. No kidding. I don't hesitate to pester my friends into buying one because which good friend wouldn't want his mates to enjoy the same life he does - trouble free. It's not an exaggeration when I say, "A mac changes your LIFE STYLE!"

That is why, I call a mac, An Elixir! An elixir to all the viral infections you might expect. A real macintosh for the crap rain you are in!

 Many people around me mistake me for an Apple evangelist. Unfortunately, I don't go behind brands. Never. I just go behind the best that every brand has to offer! :)

'Move' with automator

Automator : Create automations without programming

As simple as it might be, yes automator is a over looked, under estimated tool available in Mac OS X. 

Any one with no programming knowledge too can with point-and-click knowledge can create workflows to achieve almost anything. Although personally, I'd recommend it as a great tool for repetitive tasks such as renaming, etc! Or some task that's not repetitive in a single stretch but something that you might perform now and then like backing up your data, etc.

Here are the basics. You create a workflow that's more like flow chart. Top to bottom, the actions that you define are executed, with one's output being sent to the next on the line.

Actions are categorized on the left most (library) pane, shown in the screenshot below. The actions under the selected category are in the pane to the right of it.

Nothing gets easier than using an example: the one that I quoted in my previous post: Moving files under multiple folders into a single folder.

In our scenario, the folder named 'Jdownloads' contains 11 folders named as

Ubisoft E3 2010 Conference [Part 1 of 11] - Child of Eden(HQ)

...

Ubisoft E3 2010 Conference [Part 11 of 11] - Michael Jackson The Game

The contents of these must be moved to 'E3 Conference'. A mundane task that I hate to do with all those mouse clicks or key board hits (I mostly use the keyboard). Whichever way, I HATE to do this!

So define the 3 actions shown in Fig. 1. 

1. Find Finder Items     ---- (A1)
2. Get Folder Contents ---- (A2)
3. Move Finder Items   ---- (A3)

A1:

This action can be customized with the search options it provides. It under the hood just uses the 'search' Mac provides. So am gonna just search for the 11 folders. How do I do that? 

Look under the Jdownloads folder, for 'folders' that contain the text 'e3' in the name. The action and it's results on single-stepping are shown below. Don't be flabbergasted by the result: 12 folders. The extra 12th is the output folder. No harm done. It's empty anyway :)

A2:

Iterate through all the folders of the previous result and get their contents. In this case, 1 file in each foler adding up to 11 files.

A3:

Move the items to the specified folder!

As simple as that. Now, I could've also deleted the source folders after the move. But why don't you just try that, hands-on!

Automator to the rescue

    The long awaited E3 conference is here and I couldn't wait to watch Ubisoft's stall & developers staging its latest mind-blowing games! Wow! Assassin's creed bloodlines is going to awesome & a new Michael Jackson game for fans is rolling out soon! (For those of you wondering what this E3 conf is... it's all about games - Hardware & software. Why don't you follow the wiki link or E3's link?)

Jdownloader helped me persist the youtube videos in my HDD to watch later. The low quality videos (all except AC Brotherhood in HD ;-)) were downloaded, thanks to JD. Problem popped up when each single video was individually downloaded into a separate folder. Now I have to move every little file into some folder, say 'E3 Conference'. Or..... why not use automator of Mac OS X!

For newbies, Automator is an app that can be used to automate your jobs. (Now, Cool down! I know that didn't help! ;-)) A simple example: Remember that hundreds of pics that you captured on a tour and wanted to rename them one by one. It must've been exhausting... You thought of completing it later. Only that later never came.  Things like that can be done easily.

Our problem definition again: 11 videos. 11 separate files in 11 different folders. I hate too much branching (folders here).

Expected results: 11 videos in 1 folder.

You know the usual solution of course(Drag, drop, delete)! Now to the automator kinda solution!

To give you a clear picture: Here's how the folder looks before running the automator workflow.

And here's how it looks after moving them!

Here's the tiny workflow with just 3 actions that achieved this!

If that doesn't make sense, no worries! The following post will clear the fog!

Python: Module search path

When a module named spam is imported, the interpreter searches for a file named spam.py in the current directory, and then in the list of directories specified by the environment variable PYTHONPATH. This has the same syntax as the shell variable PATH, that is, a list of directory names. When PYTHONPATH is not set, or when the file is not found there, the search continues in an installation-dependent default path; on Unix, this is usually .:/usr/local/lib/python

Actually, modules are searched in the list of directories given by the variable sys.path which is initialized from the directory containing the input script (or the current directory), PYTHONPATH and the installation- dependent default.

Now what if you have not specified PYTHONPATH during installation? How do I edit it?

Suppose, I have my module spam.py in ~/geekcode/python. I have my other program user.py that needs to the aforementioned module.

This module search path is comparable to CLASSPATH in java.

To add ~/geekcode/python to PYTHONPATH, in your interactive mode of the Python interpreter, edit the path variable in the sys module.

>>> import sys

>>> sys.path

Printing sys.path as shown above will show up your current PYTHONPATH.

This sys.path is just another mutable python list. Hence you can easily edit it using the usual list methods, here, the append method.

sys.path.append("/Users//geekcode/python")

The only drawback of this method is that, this setting is forgotten once you restart the interpreter. 

To persist this setting, you can use the '.pth' file.  A '.pth' file with any name like 'foobar.pth' can contain any number of newline separated list of paths you need to add to PYTHONPATH aka path aka sys.path variable. It is similar to .bash_profile or .profile files of Unix systems. The paths in .pth files are added automatically to the PYTHONPATH variable whenever the interpreter restarts.

All said, now the question is, "Where do I place this .pth file?". It can be placed in any path that is already mentioned in sys.path! EASY!

Eclipse - code formatting for Beginner!

First things first! Eclipse is a Open source IDE, an Integrated Development Environment for development using languages like C, C++, PHP (both dynamic and static) for different platforms like mobile, embedded, thick and thin servers!

Two Myths broken!
1. It doesn't come with the development kit unlike Visual studio!
2. It is not for just Java.

So, with the SDK pre-installed on your machine, run your copy of eclipse that you can download for free at the eclipse project website.

This post will hence discuss about the Eclipse for J2SE although most features are same in J2EE version too!

One most important issue most developers like me spend time on is not on the code-logic but the alignment of the code! :)

So here's what you hate when you write your code in Eclipse - The alignment of the braces!

class HelloWorld{
   public static void main(String[] args){
       System.out.println("Hello World");
   }
}

which we always like to see as,

class HelloWorld

{

   public static void main(String[] args)

   {

       System.out.println("Hello World");

   }

}

Eclipse says YES to you! Go to the preferences dialog (Cmd + , in the mac) and search for 'formatter' in the filter text-box or browse your way through Java > Code Style > Formatter.

There you have it! Click edit and you can change EVERY aspect of code formatting from indentation to how your comments appear in your code window!

You might be interested in setting your braces as shown below: (The changes your make are immediately reflected on the preview pane on the right. This comes real handy!)

Also for beginners, this might be useful!

Unlike Visual studio, the code that you type in Eclipse is not auto formatted when you type the code, letting the choice to be yours!

If you want a section formatted properly, after typing in a hurry, you can at anytime select just the section  and hit cmd+shift+f to format it or without a select, if you perform the same command, the entire code is formatted.

You can also correct indentations alone with cmd + i. You can find these under the source menu in Eclipse!

Some handy vi args!

Say you compiled a program called test.cpp and the compiler spitted the error

"test.cpp:97: error: ‘itoa’ was not declared in this scope" 

at you!

Mostly, you do one of the following!

Open the file and 

a) Scroll through it!  (See line numbers with :set number  or   :set nu )

b) Jump to line 97 which you can achieve by 

i) 97G   (vi command itself)

ii) :97 enter  (ex editor command inside vi)

You can achieve this easily with the command line args itself (those that are supplied when you open vi. The file name itself is one such arg)!

vi +97 test.cpp will open file with cursor at the 97th line!

Now what if you are like me and are bad with numbers? Can't remember 97?

vi +/itoa test.cpp will perform a pattern matching and will open the file at the first match. You can then use n or N to skim through the matches until you land on your line! 

Bonus tip! :) 

Ever wished vi has alt+tab (on windows/linux) or cmd+tab (on mac) to switch between two files? It has it too! :D

Just open two or more files with all the names as args to the command!

vi file1 file2 file3 file4 file5

You will be editing file1 initially!

Check which file you are editing with ex command :args or :ar 

Vi will print

[file1] file2 file3 file4 file5 

showing the current file in brackets and the entire list that you supplied!

Move around the list with :n and :N. To jump to the first file on list use :rewind or :rew and :last for the last file!

Ooops! Now to issue of concern alt+tab! 

Once you have at least once switched between the 2 files that you need to edit alternatively, use :e # to switch between files!

or simply ^^ (Ctrl + caret)

What if you have find that you need to edit file1 and file7 alternatively but forgot to open file7??? Wait! Don't quit vi!

When you are editing file1 just call in file7 with :e file7 (e for edit) and there you have it! Now use ^^!  

As mentioned in an earlier post, you can use the clipboard to move text around the files!

Though the y (yank) and p(put/paste) commands are handy you can't easily do that for multiple lines!

use :line1,line2ya  c for copying/yanking multiple lines (where line1 = starting line number; line2 = ending line number; cn = a-z one letter clipboard name)

Switch to your file you want now without exiting vi and

then :pu c will put that clipboard c's content into the new file!

(A word of caution! The switching between files can happen only if the file you are editing is saved)

Now that's why vi is a Very Interactive editor!

vi has a clipboard too!

The very interactive(vi) editor has all that your GUI based editor has! Actually, it has more! Adding to all the basics, here are some key-taps that can help u tap the power of VI.

When you hit 'd' based delete commands like 'dd', 'nd' ... or 'y' based yank commands all that's is deleted or yanked is stored in a buffer. (Ssh! Deleting with d is not delete, it's actually 'cut'. Try 'p'-ing to paste after 'd' :) )

So where does it actually get stored? It's not one but 2 buffers!

Deleted lines are stored in a numbered buffer, named from 1 to 9. (stack like. recent entry is 1, oldest being 9)
You can yank/delete into alphabetically named buffers too (a-z).

"(double quote) is used to access this a-z buffer.

" is the simple syntax

Eg: "c5dd will delete/cut 5 lines in to buffer named 'c'

(simply 5dd will not cut into the buffer)

Interesting part is "C3dd will append your now-deleted 3 lines to your previously present contents of buffer 'c'. (Note the upper case.) You can't do this even in MS word!!!

Paste the buffer using "cp     ( "c for accessing buffer and p for paste/put )


Same works for yanking too!

To access the numbered, deletion buffer, use "np where n is number 0-9 similar to a-z.

Ain't that something!!!!

Algorithm to convert given SQL Query to Relational Algebra

For the benefit of those who were looking for a logic on how to go ahead and implement this for lab exercise.

- My program will take a SQL Query as one whole string in the command line.
- splitInputQuery will split the SQL Query based on space.
- parseSQLQuery will take one word at a time from the SQL Query and set some global flags.
- decideRelAlgebra will make a decision on what could be the Relational Algebra equivalent based on the flags set in parseSQLQuery.

Eg:
SQL: "select * from E"
RA: PROJECT E

SQL: "select name from student"
RA: PROJECT name student

SQL: "select * from student where name=neo"
RA: SELECT name=neo student

SQL: "select name,roll_no from student where name=neo"
RA: PROJECT name,roll_no(SELECT name=neo student)

Having shown the examples above, I am giving the algorithm(in the form of pseudocode) below. Hope its useful. Questions are welcome.

/Algorithm/
Algorithm used to convert simple SQL query to Relation Algebra:

/**********************************************************************************
* Description: This program is intended to take simple SQL queries and
* convert them to equivalent Relational Algebra
*
* Input: SQL Query as a single string Eg: "select emp_name from E"
*
* Output: Equivalent Relational Algebra Eg: PROJECT emp_name E
*
*********************************************************************************/
main(String[] args)
if (args.length <0)
return 0;
else {
/* args[0] will have the SQL Query */
if (splitSQLQuery(args[0]) == 0) {
call parseSQLQuery()
}
call decideRelAlgebra()
}

/**********************************************************************************
* Description: This procedure takes a simple SQL queries and split it based on space
* and stores them as a array of string
*
* Input: SQL Query as a single string Eg: "select emp_name from E"
*
* Output: split SQL Query as a array of Strings Eg: {"select" ,"emp_name","from","E"}
*
*********************************************************************************/

splitSQLQuery(inputSQLQuery) {
if (inputSQLQuery != null) {
/* if input is valid then split based on " " and save it in global array splittedInputQuery
splittedInputQuery = inputSQLQuery.split(" ");
} else {
return 1; /* return non-zero on error */
}
return 0;
}

/**********************************************************************************
* Description: This procedure takes split SQL Query array and parse them to find the
* equivalent Relational Algebra
*
* Input: Splitted SQL Query array
*
* Output: global flags are set to make a decision
*
*********************************************************************************/

parseSQLQuery() {
/* for all the strings in the splitedInputQuery do this */
for(int i 0 to no_of_strings in query) {
/* querystring is the current string form the splittedinputquery array */
if (querystring matches "select") {
/*then it could be select or it could be project in RA*/
set maybeProject to 1
continue to get next string;
}
if(querystring matches "*") {
set selectall to 1;
continue to next string;
}

if (querystring is of the pattern [a-zA-Z_]*) and (selectall != 0) {
set maybeAttribs to 1;
attribs = querystring;
continue to next string;
}
if (querystring matches "from") {
set maybeFrom to 1;
continue to next string;
}

if(querystring is of pattern [a-zA-Z-]*) and (maybeFrom is set) {
set maybeTable to 1;
tableName = queryString;
continue to next string;
}

if(querystring matches "where") {
set maybeSelect to 1
set gotWhere to 1
continue to next string;
}
/* to match with where patterns like Eg: name=N or roll_no=100 and so on
if(queryString is of pattern [a-zA-z_< > = <= >= !=0-9*]*) and (where is set to 1) {
set maybeConditions to 1
conditions = queryString;
continue to next string;
}
}
}

/**********************************************************************************
* Description: This procedure decides on the equivalent relational algebra for the given
* SQL Query based on the flags set by parseSQLQuery
*
* Input: SQL Query as a single string Eg: "select emp_name from E"
*
* Output: Equivalent Relational Algebra Eg: PROJECT emp_name E
*
*********************************************************************************/

decideRelAlgebra() {
if (gotWhere is not 1) {
set confirmedProject to 1
set relAlg to PROJECT
}
if (selectAll is 1) and (gotWhere is not 1) {
set confirmedProject to 1
set relAlg to PROJECT
}
if (gotWhere is 1) and (attribs is not null) {
set projectwithselect to 1
set relAlg to PROJECT (SELECT )
}

if (gotWhere is 1) and (selectall is 1) {
set confirmedproject to 1
set relAlg to SELECT
}
}

Very Interactive(VI) editor commands

This has been a request from couple of people, putting it down for them and for everyone who is looking for frequently used vi editor commands.

Edit commands:
-------------------
x - delete one character at a time
nx - delete n characters at a time, replace n with number you want
dd - delete/cut a line
ndd - delete/cut x lines (replace n with number you want Eg: 10dd would delete 10 lines)
yy - yank a line(copy to clipboard)
nyy - yank n lines(replace n with number you want Eg: 10yy would yank 10 lines)
p - paste from the clipboard(deleted lines are like copy too, they will be in clipboard, so p after dd or yy will paste whats there in the clipboard)

*Remember: All the above commands are relative to the current cursor position. i.e. If you are at line 20 and performing dd, line at that position will be deleted/cut. Similarly p operation will paste after 20th line.

More Edit commands:
--------------------------
dw - delete/cut a word
ndw - delete/cut n words (replace n with number you want Eg: 3dw will delete 2 words)
cw - change or replace word (move the cursor to the word you want to change and give cw, then type in the replacement word)
ncw - change n words at a time(Eg: 2cw will help you replace two words)
o - to insert a line below the line where the cursor is positioned
shift+o - to insert a line above the line where the cursor is positioned

Cursor positioning or movement:
---------------------------------------
<- or h - to move left -> or l - to move right
up arrow or k - to move up
down arrow or j - to move down
0(zero) - to move to the first character of the current line
$ - to move to last character of the line
w - to move cursor to the beginning of the next word
b - to move cursor to the first character of the preceding word
:0 - to move to the first line of the file(what you see here is zero)
:n - to move to the nth line of the file(replace n with number of your choice)
:$ - to move the cursor to the last line of the file

* CR- carriage return/Enter key in the keyboard

Scroll commands:
---------------------
^d (ctrl+d) - scroll half screen down
^u (ctrl+u) - scroll half screen up
^f (ctrl+f) - scroll full screen down
^b (ctrl+b) - scroll full screen up

(do it for yourself to see the difference, choose a bigger file to see the difference between these scrolls for yourself)

Search commands:
-----------------------
/string - to search for a string (replace string with your search string)
(n to find the next match, shift+n to find the previous match.

Search and Replace:
------------------------
:s/old_string/new_string - replaces the first occurrence of "old_string" with "new_string" in the current line (Eg:- :s/import/export will replace first occurrence of the word import with export in the current line)
:s/old_string/new_string/g - will replace all occurrences of "old_string" with "new_string" in the current line
:%s/old_string/new_string/g - will replace all occurrences of old_string with new_string in the file.

(**Remember everything is case sensitive here, to make your search & replace case insensitive see below)
:s/old_string/new_string/i
:s/old_string/new_string/gi
:%s/old_string/new_string/gi

see the 'i' at the end makes it case in-sensitive.

To perform search and replace between selected lines, you can use the commands below.
:l1,l2s/old_string/new_string/g - replace l1 and l2 with line numbers you want. (Eg:- :1,10s/import/export/g you know what this means... isn't it?)

Undo:
--------
u - to undo previous commands

Switching modes:
----------------------
i - insert mode
a - append mode
esc - to get out of any mode you already chosen

I will stop with these basic commands you would need to start.

In case if people need more useful commands at advance level, I will put a separate post later.

Happy VI'ing :))