Porting java methods to ruby

martin_mercy2001 · November 21, 2007, 11:00am

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

martin_mercy2001 · November 21, 2007, 11:07am

Hi,

 public char[] getTextCharacters(int [] holderForStartAndLength)
   {
   }
Could any one help me to do the same in ruby

Oh sure!

def getTextCharacters(holder_for_start_and_length)
end

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

It doesn’t matter. Ruby is a dynamic language. Please check out these
slides:

http://onestepback.org/articles/10things/

Cheers,
Peter

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

martin_mercy2001 · November 21, 2007, 11:18am

2007/11/21, Peter S. [email protected]:

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.

Could any one help me to do the same in ruby

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

martin_mercy2001 · November 21, 2007, 11:23am

Robert K. wrote:

really help you.

Could any one help me to do the same in ruby
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

martin_mercy2001 · November 21, 2007, 11:24am

On Nov 21, 2007, at 02:00 , Martin D. wrote:

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:

martin_mercy2001 · November 21, 2007, 11:41am

On Nov 21, 2007 11:23 AM, Ryan D. [email protected] wrote:

On Nov 21, 2007, at 02:00 , Martin D. wrote:
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

martin_mercy2001 · November 21, 2007, 11:48am

2007/11/21, Martin D. [email protected]:

            holderForStartAndLength[1] = pcEnd - pcStart;
                  || eventType == COMMENT
        //throw new XmlPullParserException("no content available to
    //      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

martin_mercy2001 · November 21, 2007, 11:52am

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

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

martin_mercy2001 · November 21, 2007, 11:25am

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 K. wrote:

2007/11/21, Peter S. [email protected]:
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.

Could any one help me to do the same in ruby

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

martin_mercy2001 · November 21, 2007, 12:23pm

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

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.

martin_mercy2001 · November 21, 2007, 1:47pm

On Nov 21, 2007 10:25 AM, Martin D. [email protected] wrote:

Hi peter,

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


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).

martin_mercy2001 · November 21, 2007, 1:56pm

2007/11/21, Martin D. [email protected]:

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

martin_mercy2001 · November 21, 2007, 2:45pm

Robert K. wrote:

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 W.

martin_mercy2001 · November 21, 2007, 4:31pm

2007/11/21, Jari W. [email protected]:

Robert K. wrote:

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.

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

martin_mercy2001 · November 21, 2007, 5:14pm

On Nov 21, 2007 2:44 PM, Jari W.
[email protected] wrote:

Robert K. wrote:

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.
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

martin_mercy2001 · November 21, 2007, 2:49pm

Peter H. wrote:

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 W.

martin_mercy2001 · November 21, 2007, 9:33pm

On Nov 21, 2007, at 02:41 , Robert D. wrote:

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.

martin_mercy2001 · November 21, 2007, 7:05pm

On 21.11.2007 17:13, Robert D. wrote:

ok that is not the case normally however,
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

martin_mercy2001 · November 21, 2007, 10:50pm

On Nov 21, 2007 9:32 PM, Ryan D. [email protected] wrote:

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.

martin_mercy2001 · November 22, 2007, 12:58am

Robert D. wrote:

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 would say my brain is scanning for some kind of separator, and the
space is too similar to the Rubish underscores, which (sometimes) makes
it harder than necessary IMO.
With good syntax highlighting, though, this is a non-issue.

Best regards,

Jari W.