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How to define Xtend method like: collection.retainAll(e|expression with e) ? [message #491384]

Wed, 14 October 2009 12:17

Messages: 3
Registered: October 2009

Junior Member

I want to define in Xtend a method that modify the content of a list according to a boolean expression applied to each element in the list.

Basically, I want to be able to define in Xtend a method that:
* takes a boolean expression as argument (like Collection.select)
* actually modify the provided collection (and returns Void)

I want to call this Xtend method from an Xpand template of this kind:

create Set[MyType] result getXYZ(MyOtherType this) :
result.retainAll(e|e.associationFromMyType == this);

And I don't know how to define such a parameter in Xtend:

Void retainAll(Collection this, ??? conditionArgument) :
let temp = this.select(conditionArgument) :
?set this to temp?;

Is this any possible?

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Re: How to define Xtend method like: collection.retainAll(e|expression with e) ? [message #491388 is a reply to message #491384]

Wed, 14 October 2009 12:19

Sebastian Zarnekow

Messages: 3118
Registered: July 2009

Senior Member

Hi C,

the higher order collection functions are hardcoded. It is currently not
possible to declare and implement something similar in your own extensions.

Sorry for inconvenience,
Sebastian
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C schrieb:
> I want to define in Xtend a method that modify the content of a list
> according to a boolean expression applied to each element in the list.
>
> Basically, I want to be able to define in Xtend a method that:
> * takes a boolean expression as argument (like Collection.select)
> * actually modify the provided collection (and returns Void)
>
> I want to call this Xtend method from an Xpand template of this kind:
>
> create Set[MyType] result getXYZ(MyOtherType this) :
> result.retainAll(e|e.associationFromMyType == this);
>
> And I don't know how to define such a parameter in Xtend:
>
> Void retainAll(Collection this, ??? conditionArgument) :
> let temp = this.select(conditionArgument) :
> ?set this to temp?;
>
> Is this any possible?

Report message to a moderator

Re: How to define Xtend method like: collection.retainAll(e|expression with e) ? [message #491391 is a reply to message #491388]

Wed, 14 October 2009 12:35

Messages: 3
Registered: October 2009

Junior Member

Hi Sebastian, thanks for fast answer.

Would it be possible then to subclass the java code that implements it?

What is the Java class that implements the high order collection functions?

Cheers,
Cédric

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Re: How to define Xtend method like: collection.retainAll(e|expression with e) ? [message #491509 is a reply to message #491391]

Wed, 14 October 2009 20:25

Sven Efftinge

Messages: 1823
Registered: July 2009

Senior Member

It's not possible to introduce new higher order functions, since
you'ld have to extend the parser.

Maybe

result.removeAll(result.select(e|e.associationFromMyType != this));

is sufficient?

Cheers,
Sven

C schrieb:
> Hi Sebastian, thanks for fast answer.
>
> Would it be possible then to subclass the java code that implements it?
>
> What is the Java class that implements the high order collection functions?
>
> Cheers,
> Cédric

--
Need professional support for Eclipse Modeling?
Go visit: http://xtext.itemis.com

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