porting java methods to ruby

M

Martin Durai

could any one help me out to solve this.

Following is a function java

Actually the following function has a character array as a return type

public char[] getTextCharacters(int [] holderForStartAndLength)
{
}

Could any one help me to do the same in ruby


Thank you in advance
 
P

Peter Szinek

R

Robert Klemme

2007/11/21 said:
Hi,
public char[] getTextCharacters(int [] holderForStartAndLength)
{
}

This won't even compile because there is no "return" statement. Also,
using an array to pass two values is at best sub optimal. And since
you do not provide any details about the class at hand nobody can
really help you.
Oh sure!

def getTextCharacters(holder_for_start_and_length)
end

LOL

Actually, we can make this even *more* rubyish:

def get_text_characters holder_for_start_and_length
end

:)

Cheers

robert
 
P

Peter Szinek

Robert said:
2007/11/21 said:
Hi,
public char[] getTextCharacters(int [] holderForStartAndLength)
{
}

This won't even compile because there is no "return" statement. Also,
using an array to pass two values is at best sub optimal. And since
you do not provide any details about the class at hand nobody can
really help you.
Oh sure!

def getTextCharacters(holder_for_start_and_length)
end

LOL

Actually, we can make this even *more* rubyish:

def get_text_characters holder_for_start_and_length
end

Ah, thanks Robert :) The most trivial tasks are the easiest to screw
up, right?

___
http://www.rubyrailways.com
http://scrubyt.org
 
R

Ryan Davis

Actually the following function has a character array as a return type

public char[] getTextCharacters(int [] holderForStartAndLength)
{
}


Having done far too much of this recently, my guess is it'll look
something like:
def get_text_characters
result = []

# get the characters and start from whatever...

return result, start
end

I ignored the holderForStartAndLength because the name hints that they
are a stupid java hack for not having rich return values. In
get_text_characters we don't bother with length because our array (or
string... depends on how you actually want to use it) knows it's
length and we return the start offset with it. You'd call it like:
 
M

Martin Durai

Hi peter,

i have attached my java code which i have to port to ruby. could you
help me with this

public char[] getTextCharacters(int [] holderForStartAndLength)
{
if( eventType == TEXT ) {
if(usePC) {
holderForStartAndLength[0] = pcStart;
holderForStartAndLength[1] = pcEnd - pcStart;
return pc;
} else {
holderForStartAndLength[0] = posStart;
holderForStartAndLength[1] = posEnd - posStart;
return buf;

}
} else if( eventType == START_TAG
|| eventType == END_TAG
|| eventType == CDSECT
|| eventType == COMMENT
|| eventType == ENTITY_REF
|| eventType == PROCESSING_INSTRUCTION
|| eventType == IGNORABLE_WHITESPACE
|| eventType == DOCDECL)
{
holderForStartAndLength[0] = posStart;
holderForStartAndLength[1] = posEnd - posStart;
return buf;
} else if(eventType == START_DOCUMENT
|| eventType == END_DOCUMENT) {
//throw new XmlPullParserException("no content available to
read");
holderForStartAndLength[0] = holderForStartAndLength[1] =
-1;
return null;
} else {
throw new IllegalArgumentException("unknown text eventType:
"+eventType);
}
// String s = getText();
// char[] cb = null;
// if(s!= null) {
// cb = s.toCharArray();
// holderForStartAndLength[0] = 0;
// holderForStartAndLength[1] = s.length();
// } else {
// }
// return cb;
}

All these code comes unde java version of pull parser

Robert said:
2007/11/21 said:
Hi,
public char[] getTextCharacters(int [] holderForStartAndLength)
{
}

This won't even compile because there is no "return" statement. Also,
using an array to pass two values is at best sub optimal. And since
you do not provide any details about the class at hand nobody can
really help you.
Oh sure!

def getTextCharacters(holder_for_start_and_length)
end

LOL

Actually, we can make this even *more* rubyish:

def get_text_characters holder_for_start_and_length
end

:)

Cheers

robert
 
R

Robert Dober

Actually the following function has a character array as a return type

public char[] getTextCharacters(int [] holderForStartAndLength)
I do not like this ---------------------------------^

def get_text_chars start=0, length=1

IOW you cannot port Java to Ruby, it will remain Java in disguise.

Robert
 
R

Robert Klemme

2007/11/21 said:
Hi peter,

i have attached my java code which i have to port to ruby. could you
help me with this

public char[] getTextCharacters(int [] holderForStartAndLength)
{
if( eventType == TEXT ) {
if(usePC) {
holderForStartAndLength[0] = pcStart;
holderForStartAndLength[1] = pcEnd - pcStart;
return pc;
} else {
holderForStartAndLength[0] = posStart;
holderForStartAndLength[1] = posEnd - posStart;
return buf;

}
} else if( eventType == START_TAG
|| eventType == END_TAG
|| eventType == CDSECT
|| eventType == COMMENT
|| eventType == ENTITY_REF
|| eventType == PROCESSING_INSTRUCTION
|| eventType == IGNORABLE_WHITESPACE
|| eventType == DOCDECL)
{
holderForStartAndLength[0] = posStart;
holderForStartAndLength[1] = posEnd - posStart;
return buf;
} else if(eventType == START_DOCUMENT
|| eventType == END_DOCUMENT) {
//throw new XmlPullParserException("no content available to
read");
holderForStartAndLength[0] = holderForStartAndLength[1] =
-1;
return null;
} else {
throw new IllegalArgumentException("unknown text eventType:
"+eventType);
}
// String s = getText();
// char[] cb = null;
// if(s!= null) {
// cb = s.toCharArray();
// holderForStartAndLength[0] = 0;
// holderForStartAndLength[1] = s.length();
// } else {
// }
// return cb;
}

All these code comes unde java version of pull parser

First of all I would create a class for the return values, like

TextSubRange = Struct.new :text, :start, :end

Then I would change all the if (x==..||x==...) to use a case statement.

Btw, I would do the same to the Java code (i.e. create another class
and use "switch").

Cheers

robert
 
M

Martin Durai

Thank you robert,


my task is to port java classes and methods to ruby just like tha above
one.

could you help me with this porting
 
P

Peter Hickman

The simplest conversion is this:

def getTextCharacters(holholderForStartAndLength)
case @eventType
when TEXT
if @usePC
holderForStartAndLength[0] = @pcStart
holderForStartAndLength[1] = @pcEnd - @pcStart
return @pc
else
holderForStartAndLength[0] = @posStart
holderForStartAndLength[1] = @posEnd - @posStart
return @buf
end
when START_TAG, END_TAG, CDSECT, COMMENT, ENTITY_REF,
PROCESSING_INSTRUCTION, IGNORABLE_WHITESPACE, DOCDECL
holderForStartAndLength[0] = @posStart
holderForStartAndLength[1] = @posEnd - @posStart
return @buf
when START_DOCUMENT, END_DOCUMENT
holderForStartAndLength[0] = holderForStartAndLength[1] = -1
return nil
else
raise "unknown text eventType: " + @eventType
end
end

Of course this is untested and assumes that the class that defines it
will also set up the various class variables (the @something in the
code) and the constants (the SOMETHING in the code). You should also
consider creating your own exception class for the raise.

Please also read "Pounding A Nail: Old Shoe or Glass Bottle?" by Alex
Papadimoulis at
http://weblogs.asp.net/alex_papadimoulis/archive/2005/05/25/408925.aspx

Why the hell are you not using an existing ruby xml library, you know
that your's will be the slowest xml parser on earth?

This endeavour is made of fail.
 
R

Richard Conroy

Hi peter,

i have attached my java code which i have to port to ruby. could you
help me with this

<code snipped>

I would refactor that code before you consider porting it to anything. Theres
a lot of external dependencies and a lot of unsafe constructs. That single
function uses the following instance members:
usePC
eventType
pcStart
pcEnd
posStart
posEnd
pc
buf
getText

You are also not doing a lot of input value checking, and the function is very
non-DRY. All of the return values are side effects of the method,
defined elsewhere.
The position holder (the function argument) should be a class.

However its par for the course in Java really. However even in Java you would
find that function very difficult to unit test without complex mocking.

You would never write a Ruby function that behaved like that. You would break
up the responsibilities of the function into individual pieces
(functions), then take advantage
of Ruby's better literal syntax and conditionals to clear up the messy
conditionals.
(The Ruby switch statement is a thing of beauty).
 
R

Robert Klemme

2007/11/21 said:
Thank you robert,


my task is to port java classes and methods to ruby just like tha above
one.

could you help me with this porting

Sorry, you'll have to do the typing yourself. If you insist on an
exact copy then that's not really that difficult, there are arrays and
Strings etc.

robert
 
J

Jari Williamsson

Robert said:
Actually, we can make this even *more* rubyish:

def get_text_characters holder_for_start_and_length
end

Is it actually more rubyish to omit the parenthesis? I often find it
much harder to read, specially in e-mails with a variable-spaced font.

Best regards,

Jari Williamsson
 
J

Jari Williamsson

Peter said:
The simplest conversion is this:
[...]
holderForStartAndLength[0] = @pcStart
holderForStartAndLength[1] = @pcEnd - @pcStart

I would probably write something like:
holder_for_start_and_length = [@pcStart, @pcEnd - @pcStart]

Best regards,

Jari Williamsson
 
R

Robert Klemme

2007/11/21 said:
Is it actually more rubyish to omit the parenthesis? I often find it
much harder to read, specially in e-mails with a variable-spaced font.

I left that to optimize for someone else. ;-)

Seriously: most of the time I use brackets in method definitions - not
necessary usages.

Kind regards

robert
 
R

Robert Dober

Is it actually more rubyish to omit the parenthesis? I often find it
much harder to read, specially in e-mails with a variable-spaced font.
ok that is not the case normally however,
Nevertheless most people still think it is terrible (e.g. David
Black), I believe - and some others, Ara IIRC - believe it is much
easier to read.

Consider this, your brain has not yet used to missing parens, and it
is actually looking for them, that already is some unnecessary work,
right ;).
I really would love to know if Smalltalkers feel the same when they
see Ruby using minium parens style, Rick?

I guess I would use parens if I were paid to write Ruby and somebody
paying askes me nicely (like "or you will get fired").
So somebody ready to pay??? ;)

Cheers
Robert
 
R

Robert Klemme

ok that is not the case normally however,
Nevertheless most people still think it is terrible (e.g. David
Black), I believe - and some others, Ara IIRC - believe it is much
easier to read.

Consider this, your brain has not yet used to missing parens, and it
is actually looking for them, that already is some unnecessary work,
right ;).
I really would love to know if Smalltalkers feel the same when they
see Ruby using minium parens style, Rick?

I guess I would use parens if I were paid to write Ruby and somebody
paying askes me nicely (like "or you will get fired").
So somebody ready to pay??? ;)

No, but I can ask you nicely. :)

Seriously: it just occurs to me that the topic of using or not using
parens seems to come up much less frequently than the topic of whether
to use curly braces or "do end" with blocks. Maybe that's an indication
that people faster adjust to the missing parens, dunno.

Kind regards

robert
 
R

Ryan Davis

public char[] getTextCharacters(int [] holderForStartAndLength)
I do not like this ---------------------------------^

def get_text_chars start=0, length=1

IOW you cannot port Java to Ruby, it will remain Java in disguise.

nonsense... you can port it just fine if you allow for design changes.
that is why I didn't pass in start or length at all... they're RETURN
values, not arguments.
 
R

Robert Dober

public char[] getTextCharacters(int [] holderForStartAndLength)
I do not like this ---------------------------------^

def get_text_chars start=0, length=1

IOW you cannot port Java to Ruby, it will remain Java in disguise.

nonsense... you can port it just fine if you allow for design changes.
that is why I didn't pass in start or length at all... they're RETURN
values, not arguments.
Ryan we are not going to write Java code in Ruby only because it can
be done, are we?
Probably I was not clear, of course you can Java code in a way that
the Ruby interpreter produces the same results, but does this make it
Ruby code?

R.
 
M

MenTaLguY

Ryan we are not going to write Java code in Ruby only because it can
be done, are we?

IMO, Ryan's example was farthest from writing Java in Ruby of all the
examples given in this thread.

-mental
 

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