Saturday, March 19, 2011

My First Ruby Program (pt. 1 in a series)

I've decided to chart my progress on picking up Ruby as a programming language.

The first program I was going to go for is a program that reverses text.When I worked with graphics, I found that many times Arabic and Hebrew texts ended up being reversed. Because while they are written from right-to-left, these languages are displayed in special ways by Word Processing programs. They allow you to enter the text as it'd would be written, but save left-to-right, so that when you copy the text to a program that can't display the text in reverse order, they end up backwards.

This is such a common problem that most modern graphic programs (like GIMP) now allow you to enter text in both left-to-right as well as right-to-left order. But not all and not old ones. So what I want is to make a program that will take a text file and reverse the order of each line without reversing the order of the lines. Structurally this is quite simple you take each character put it in a stack and then write them out in the last-one-in, first-one-out order like you were putting each character in a bag and then taking it out. But I wanted to do this in object-oriented mode.

So here's what I've got so far:


First thing I learned that made me super happy is that there is a method in Ruby called reverse, that lets you reverse the text without having to do the stack step by step nightmare (like you would have to in say pure C or a lower level language like Assembly).

The first line require 'rubygems' calls another library but I'm not using it, I just saw it and though I better put it in, in case I need it. Then we get to the line that was missing the first time I wrote this program: text = Object.new Here we create the variable, we make it an object (so it can have a reverse method in it!) and this is the step I was missing till today.

The rest is a little fun piece of code I learned yesterday.

Dir["ToReverse-*.txt"].each do |filename|

This calls the Dir class method to look for all files in that folder (in the same Directory, get it?) that are prefaced with "ToReverse-" and end it ".txt" and will spit-out the filename of each one. Then to each one it will get the file name assigned to a transitory variable called filename.
text = File.read( filename )
Here I have the text object be filled up with the contents of each file. Which works fine for one file, but not sure what happens with more than one. Time to experiment. 

The rest of it merely calls the reverse method with imperative (the exclamation mark means the text variable will get re-written by the output). Out puts text then ends the loop.

What I want to do next is cut up the string at the line breaks and spit it into an array so that each element in the array is a line. Reverse each line then either print the array or write it to a file. But first I gotta figure out why the output screws up Hebrew.

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