Monday, September 20, 2010

Faith - Forced and Free

Some people just never step down from this moral high ground of insisting that everyone else believe the same as he/she does. And they are willing to use force to make sure that their dreams come true.

This is especially true of people that everyone should follow one religion, in the case of Maldives Islam.

It is true that the Maldivian constitution says that all citizens should be Muslims, which brings us to the notion of so called 100% Islamic country. Just because it is written in a legal document does not make it true. If it was the case, the world over would have solved all problems of poverty, crime, etc. It will only be a matter of writing 'everyone in Maldives is above poverty level' in the constitution, problem solved!

Some say, we should revoke the citizenship of people who become apostates or worse killed (let alone the fact that death penalty for apostasy is a debatable issue). So by that logic, to make Maldives a 0% poverty nation, we can revoke the citizenship of people who fare below the poverty line. To make 0% crime/fraud/corruption nation, we can revoke the citizenship of criminals, fraudsters and corrupt people (hmm, come to think of it, that would get rid of most of the politicians).

The fact of the matter is, by definition, faith is something that comes when someone wholeheartedly accept and believe. It can come only through conviction. This can only happen when a person is free to believe. When he is forced, then he can only act like he believes. This only creates a hypocrite out of him, and we have plenty of that in this country.

When you really look, it is precisely the freedom of conscience that enables you, me and everyone else to be Mulsims too. It just happens that this freedom of conscience is not protected for people who hold a belief that is different from majority backed state mandated belief.

If one day Maldivian constitution states "...Maldives must be 100% christian.." or atheist or buddists and enforced by force of law, it will be the day Muslim scholars (& majority of maldivians) of this country advocate for religious freedom. Its a pity that they don't realize its just the other side of the same coin that some are living in already.

Those who advocate faith by force, should consider the day when the force is not with you. When people of different belief have that force (via majority or whatever), is it ok for them to impose their own belief by force?

Friday, September 10, 2010

Using perl and awk for data extraction - Part 3

In part 2, you saw the small perl program written to extract data. The code uses fair amount of one-liners and perl syntactic sugar. In addition, it uses functional style of programming where appropriate.

Lines 1-13:
Just startup lines and variable declarations. You could use variables without declaring first.

Line 18:
@userinput = <> 

This grabs contents from standard input and store in array @userinput. The <> actually grabs the whole content to memory, be it file or from standard input. This is not advisable to be used in production code.

Line 21:
$colheader = shift(@userinput)

This grabs the first item from array @userinput using the shift function. It also reduces the number of elements in @userinput.

Line 22:
chomp($colheader)

The first line stored in $colheader contains the newline character as well. This newline character is removed with the chomp function. Strictly speaking, it removes the input record separator as specified in perl special vairable $/, which by default is newline character.

Line 23:
my @cols = split(",", $colheader)

Splits the contents of $colheader based on delimeter ,(comma). The split function returns an array of strings. This gets stored in @cols, resulting in @cols containing the column names.

Line 27:
$colist = join('', map {$i++ ; "-v $_=$i "} @cols)

This line consists of two parts, firstly the use of map function, and secondly the use of join function.
The map function, "maps" or applies a given function to each member of a list. Suppose you have a line that says (where @numbers = (1, 2, 3, 4)):
@results = map(square, @numbers)

This will apply the function 'square' to each member of the array @numbers. The result will be an array of elements that contain (square(1), square(2), square(3), square(4)). If square is a function that returns the mathematical square of its arguments, then @results will contain (1, 4, 9, 16).
Similarly, instead of a function, you can give a code block within curly braces {}, to be applied to each member of the array given. In this case the code block is
{$i++; "-v $_=$i "}

Note the trailing space just after i. This means, for each element in @cols, run the piece of code in the curly braces. The code in curly braces does two things:
1. increment variable i
2. returns a string of the form "v = $_=$i "
In perl, $i occurring within double quoted text strings will be parsed and hence its value will be substituted. $_ is the perl special variable that contains the current argument, ie the element from @cols that is under consideration
Suppose @cols is (length, width, height), then the result of map function will be
("-v length=1", "-v width=2", "-v height=3")

This resulting array from the map function is directly used by the join function. The join functions just 'joins' the elements of a string array separated by a given string. Here we are using the null string '' as separator, ie just directly join. As a final result, $colist will contain something like
"-v length=1 -v width=2 -v height=3"


For those interested, perl's map function is very similar to lisp's mapcar or haskell's map function.

Line 30:
my $cmd = "|awk -F, -v OFS=',' $colist '$cond { print $ext }'" 

This builds a command line syntax for calling awk from perl. Note the use of unix pipe | at the beginning. This will cause whatever we send to be piped to awk program. -F, specifies that field separator is ,(comma) and -v OFS=',' specifies that output field separator to be used is also comma. Since this is a double quoted string, $colist is parsed and its value is substituted, rather than the literal $colist. Same for $cond and $ext.

Line 33:
open (AWK, $cmd)

This is perl standard way of calling shell commands. You could use ABC, BLAH, FOOBAR or anything instead of AWK.

Line 34:
map {print AWK} @userinput

Here again I use perl's ability to do functional programming. It runs the code {print AWK} to each element in the array @userinput, ie it sends each line in @userinput to the command shell as specified in line 30.