From: Gawnsoft <xlucid@...>
Date: 2003-08-01T13:26:37+09:00
Subject: A bundle of newbie queries

I've finally overcome my newbie embarrassment enough to post about
actual code 

--------------------

After a couple of years(!) of about-to, I finally leapt over enough
conceptual hurdles to use Ruby for something.  (RubyWin 0.0.3.5, with
Ruby 1.6.4)  (And thank you Dave and Andy for providing the book with
the distro)

I was really quite insanely pleased that my first use of Ruby did
something really quite involved - it counts the number of unique IP
addresses of people who have downloaded a particular file from my
web-server -  and did it in four lines of code!

   aFile = File.open('D:/Data/Logs/Savant/copyOfGeneral.txt')

   aDictionary = Hash.new

   aFile.each_line { | line | aDictionary[line.slice(/[0-9.]+/)] = 1
if line.include?("plastic_1.1_lite-UMLtool-fw.exe") }

   puts aDictionary.size

And then I amended it to tell me how often the file was downloaded
from each unique IP address by changing the following lines to:

   aDictionary = Hash.new(0)

   aFile.each_line { | eachLine | aDictionary[ /[0-9.]+/ ] =
aDictionary[ /[0-9.]+/ ] + 1 if
eachLine.include?("plastic_1.1_lite-UMLtool-fw.exe") }

All well and good - and I was surprised how quickly I got my head
round file handling, hashes and regular expressions, and delighted at
the way I could use a regexp as the index of a hash.

(Btw, the file in question is a quite competent little UML diagramming
tool - freeware, for Windows, less than 2MB, which autogenerates Java
stub code.  If anyone is interested in that sort of thing, it's
available from the Smalltalk links page in my sig)

I have some fresh and queries and problems though - 

1) After the file has been opened and I've iterated through it once, I
can't successfully iterate through the opened file for something else.
e.g. 

   dictionary2 = Hash.new(0)

   aFile.each_line { | eachLine | dictionary2[ /[0-9.]+/ ] =
dictionary2[ /[0-9.]+/ ] + 1 if eachLine.include?("anotherfile") }

-----------

2) I then tried to get the no-longer usable file garbage-collected by
IRB-ing

   aFile = nil   

but even after evaluating this statement, another windows app still
fails to be able to over-write copyOfGeneral.txt 

What should I do to get Ruby to 'free up' the file?

-----------
3) I tried to cut it down from 4 lines of code to 3 lines of code by
using:
   (File.open("d:/Data/Logs/Savant/copyOfGeneral.txt")).each_line {
|line| blah... }

I'm sure I've seen snippets of code in the newsgroup that call methods
from the result of called methods, although the real reason I tried it
is because I'm currently learning Smalltalk where 

   ( File open: "name of aFile" ) each_line: [ blah... ]     #
pseudocode only this, in all probability, btw

works as the parenthesised expression is evaluated first and returns
aFile, which is then sent the eac_line message

What are the rules as to when   object.method.method    is a valid
Ruby construct?   Is it ever a valid Ruby construct?
------------
4) I'd like to c'n'p a multi-line method into IRB all at once.  Can I?
And if so, how?

def countDownloads (aFile, aString)

  anIpNum = Regexp.new('[0-9.]+')

  aDictionary = Hash.new(0)

  aFile.each_line { | line | aDictionary[line.slice(anIpNum)] =
aDictionary[line.slice(anIpNum)] + 1 if line.include?(aString) }

  puts aDictionary.size

end
------------
5) I'd like to save this method as a .rb file, and invoke it from IRB.
How do I?
------------
6) I'd like to change the current Windows directory from within IRB.
How do I?

Using irb_context, I saw there was an irb_path set (to be '(irb)' so I
tried: conf.irb_path="d:/data/grlcode"  which returned: 
NameError: undefined local variable or method `conf' for
#<Object:0x463b638>


Cheers, 
   Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki:  http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk)  http://html.dnsalias.net/gawnsoft/smalltalk