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Define infix arithmetic operations for a custom class [message #1840045]

Tue, 06 April 2021 06:32

Denis Nikiforov

Messages: 346
Registered: August 2013

Senior Member

Hi

Is it possible to implement something like this?

transformation Test();

main()
{
    var obj := object MyClass {};
    obj * 1;
}

intermediate class MyClass { val : Integer };
	
query MyClass::*(int : Integer) : MyClass = self;

QVTo editor doesn't show an error for "obj * 1". It shows an error only for the last query.

I tried to use the following possible aliases but with no success:

query MyClass::_*(int : Integer) : MyClass = self;
query MyClass::mult(int : Integer) : MyClass = self;
query MyClass::multiply(int : Integer) : MyClass = self;
query MyClass::multiplication(int : Integer) : MyClass = self;

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Re: Define infix arithmetic operations for a custom class [message #1840046 is a reply to message #1840045]

Tue, 06 April 2021 07:07

Christopher Gerking

Messages: 116
Registered: April 2011

Senior Member

Hi

Quote:

Is it possible to implement something like this?

I'm afraid that custom infix notation is not supported.

Quote:

QVTo editor doesn't show an error for "obj * 1".

It is indeed strange that there is no error.

Quote:

query MyClass::*(int : Integer) : MyClass = self;

Why = self? I would have done it this way:

transformation Test();

main()
{
    var obj := object MyClass {};
    obj.mult(1);
}

intermediate class MyClass { val : Integer };
	
query MyClass::mult(int : Integer) : MyClass = object MyClass {
	val := self.val * int;
};

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Re: Define infix arithmetic operations for a custom class [message #1840051 is a reply to message #1840046]

Tue, 06 April 2021 07:56

Denis Nikiforov

Messages: 346
Registered: August 2013

Senior Member

Christopher Gerking wrote on Tue, 06 April 2021 12:07

It is indeed strange that there is no error.

Thanks for answer! Because of this behaviour I decided that custom infix operators are supported, and I can define them using an alias. I will use standard queries instead as you suggest.

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Re: Define infix arithmetic operations for a custom class [message #1840079 is a reply to message #1840051]

Tue, 06 April 2021 12:45

Ed Willink

Messages: 7670
Registered: July 2009

Senior Member

Hi

This is an OCL limitation.

x . name

is a PropertyCallExp, whereas

x (  ... )

is an OperationCallExp with a few magic builtin infixes.

For the Pivot-based OCL where the Standard Library has an extensible model:

	/**
	oclText[false] if either oclText[self] or oclText[b] is oclText[false].
	Otherwise oclText[true].
	**/
	operation and2(b : Boolean[1]) : Boolean[1] validating precedence=AND => 'org.eclipse.ocl.pivot.library.logical.BooleanAndOperation2'
	{
		body: if self = false then false
		      elseif b = false then false
		      else true
		      endif;
	}

The 2-valued variant of and is added using the above segment of OCL-2.5.oclstlib as an infix with AND precedence.

Sadly migration of QVTo to exploit the Pivot-based OCL is a long way away.

Regards

Ed Willink

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