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Modifying Type Declaration [message #643187]

Sun, 05 December 2010 21:19

Yiannis Gkoufas

Messages: 6
Registered: December 2010

Junior Member

Hi there!
I have read and run pretty much all of the examples I have found online, but I have failed to understand how it possible to modify compiler behaviour on Type Declaration.
Can anyone provide me with some hints?

Thanks a lot!

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Re: Modifying Type Declaration [message #643190 is a reply to message #643187]

Sun, 05 December 2010 22:12

Stephan Herrmann

Messages: 1830
Registered: July 2009

Senior Member

Hi,

I'm not sure exactly how to help:

What is your goal? Do you want to do something similar
to the examples in my blog post [1] [2] [3] ?

Also, are you looking for hints on how to apply OT/J and
OT/Equinox or are you looking for advice on how class
TypeDeclaration (in the Eclipse Java Compiler?) works and
can be modified?

best,
Stephan

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Re: Modifying Type Declaration [message #643191 is a reply to message #643190]

Sun, 05 December 2010 22:28

Yiannis Gkoufas

Messages: 6
Registered: December 2010

Junior Member

Hi Stephan,

I have studied your 3 examples but they didn't help me in my case.
I want to develop an OT plugin which makes the following enum declaration valid:

public enum enumName2 extends enumName{
three,four;
}

And, as you understand, my purpose is if the enumName is:

public enum enumName{
one,two;
}

then the enumName2 includes one,two,three,four.

Thanks!

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Re: Modifying Type Declaration [message #643319 is a reply to message #643187]

Mon, 06 December 2010 13:55

Jan Marc Hoffmann

Messages: 32
Registered: July 2009

Member

Correct me but I don't think Stephans example will apply here.

Adapting the TypeDeclaration won't be a problem but adjusting the Parser to parse your grammer might be problematic. You will have to modify the Parser logic which is generally only possible if you adjust the grammar and regenerate the logic tables used by the Parser to match your new grammar.

The only way around this would be to trick the Parser by manipulating the Scanner. This would be done the following way but is not trivial:

1. Create a ScannerAdaptor

- When the Scanner reads the 'extends' token, check if you are handling an enum and silently discard the 'extends' and the following 'TypeRef'. But keep them somwhere else. (Especially the positions)

- Activate the ParserAdaptor

2. Create a ParserAdaptor

- Adapt the Parser.consumeEnumHeader() method to handle your additional informations. (e.g. by a role of TypeDeclaration)

- Discard the enum which was referenced after the extends token.

But beware: This will only work if they are in the same CompilationUnit and in the fitting order.

If you want real "extends" behaviour (that keyword might not be fitting for your task OO-wise) you need to correctly resolve the referenced Enum. Which will be quite complicated.

So your task might be way more complicated than you first thought it might be. Depending on the priority of this one I would rather drop it. :=)

greetings

Jan Marc

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Re: Modifying Type Declaration [message #643452 is a reply to message #643319]

Mon, 06 December 2010 22:25

Yiannis Gkoufas

Messages: 6
Registered: December 2010

Junior Member

Hi Jan!

Thanks a lot for your remarks, I will start coding and see what happens! Very Happy

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Re: Modifying Type Declaration [message #643466 is a reply to message #643452]

Mon, 06 December 2010 23:46

Stephan Herrmann

Messages: 1830
Registered: July 2009

Senior Member

Yiannis Gkoufas wrote on Mon, 06 December 2010 23:25

Hi Jan!

Thanks a lot for your remarks, I will start coding and see what happens! Very Happy

Good luck

As Jan Marc correctly mentioned, an "extends" relationship
between enums could mean different things and you surely
won't get true sub-typing, e.g.

But feel free to ask more specific questions on how to
achieve the adaptation using OT/J.

best,
Stephan

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Re: Modifying Type Declaration [message #643524 is a reply to message #643466]

Tue, 07 December 2010 09:22

Yiannis Gkoufas

Messages: 6
Registered: December 2010

Junior Member

Thanks a lot all, Stephan!

My first question on Jan's suggestion is this:
when saying:
"check if you are handling an enum"

it means to wait for the enum keyword and have a flag about it or is it a more high-level way to check it?

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Re: Modifying Type Declaration [message #643629 is a reply to message #643524]

Tue, 07 December 2010 16:52

Stephan Herrmann

Messages: 1830
Registered: July 2009

Senior Member

Yiannis Gkoufas wrote on Tue, 07 December 2010 10:22

My first question on Jan's suggestion is this:
when saying:
"check if you are handling an enum"

it means to wait for the enum keyword and have a flag about it or is it a more high-level way to check it?

Detecting an enum declaration by waiting for the enum
keyword sounds pretty straight forward to me Smile

Much in line with the ScannerAdaptor from my blog post.

When you look for a more high-level way, I wouldn't
actually know which way is up.

I think Jan Marcs suggestion is pointing in a good
direction already.

Perhaps the non-obvious part is where should the
flag ("I have seen the enum keyword") be stored?
Just make it a field of the role that adapts the
Scanner, and it will be immediately available
once you see the subsequent "extends".
Only make sure you define a point where the flag
will be reset if you don't see "extends" Smile

HTH
Stephan

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Re: Modifying Type Declaration [message #644617 is a reply to message #643319]

Mon, 13 December 2010 13:45

Yiannis Gkoufas

Messages: 6
Registered: December 2010

Junior Member

Jan Marc Hoffmann wrote on Mon, 06 December 2010 08:55

2. Create a ParserAdaptor

- Adapt the Parser.consumeEnumHeader() method to handle your additional informations. (e.g. by a role of TypeDeclaration)

- Discard the enum which was referenced after the extends token.

Hi Jan!

are you sure that I have to adapt the consumeEnumHeader() method and not consumeEnumDeclaration().

Is there anywhere online code snippets of adapting consumeEnumDeclaration/Header() or consumeClassDeclaration()?

Thanks a lot!
Yiannis

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Re: Modifying Type Declaration [message #644956 is a reply to message #644617]

Tue, 14 December 2010 23:44

Stephan Herrmann

Messages: 1830
Registered: July 2009

Senior Member

Yiannis Gkoufas wrote on Mon, 13 December 2010 14:45

are you sure that I have to adapt the consumeEnumHeader() method and not consumeEnumDeclaration().

I don't think this was intended as an exact recipe Smile

So, yes, if the logic you want to insert requires that the
enum has been fully constructed then consumeEnumDeclaration()
is a better hook.

So, just go ahead, declare a callin binding to the consume
method, inspect the astStack and find the newly constructed
TypeDeclaration on top, which you may then update as desired.

cheers,
Stephan

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