Operator From()

[nerobotParticipant]

Is it a good idea to have From() operator (along with To())?
I want to union similar conversions To/From in one place, it can be possible with From operator.
Maybe I don’t know some limitation of that?

Also I want to use From as co-operator for assignment operator.

For example:

Monkey

Class Wrap<T> Field val:T Method New( val:T ) Self.val=val End Operator From:Wrap<T>( val:T ) Self.val=val Return Self End Operator To:T() Return val End End ' usage Local i1:=New Wrap<Int>( 777 ) i1=i1+222 Print i1 ' expecting 999 here

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Class Wrap<T>   Field val:T   Method New( val:T )     Self.val=val   End   Operator From:Wrap<T>( val:T )     Self.val=val     Return Self   End   Operator To:T()     Return val   End End ' usage Local i1:=New Wrap<Int>( 777 ) i1=i1+222 Print i1 ' expecting 999 here

In this example we have boxed int which behave like plain int type – and without creating new instance when assigning a value.

PS. assignment operator will use From and just reassign variable to self if we don’t create instance inside of From.

[Mark SiblyKeymaster]

I don’t like having 1001 ways to convert values as it can easily get too confusing how things work when the compiler does a ton of implicit/magic stuff behind your back. C++ is a bit like this – there’re copy ctors, assignments and cast operators (at least, probably more since c++11) all of which can result in type conversions but it’s not always obvious which one gets called or even when.

So the monkey2 equivalent might be: if ‘operator from’ WAS supported, and a dst type implemented ‘operator from’ and a src type implemented ‘operator to’, which would get used when converting from src type to dst type?

IMO, operator to plus type extensions allows you to do pretty much anything without everything getting too confusing. If there’s something you can’t do this way, let me know and we can try to come up with a solution.

For example, it allows me use std.geom types like Vec3f with assimp and bullet and have them automatically convert correctly from the native assimp/bullet geom types like aiVector3D.

And there is no overloadable assignment operator in monkey2 (or copy ctor).

[nerobotParticipant]

The truth is, I don’t want to have such magic in monkey2.

I agree – operator To + extensions = powerful coding.

So the monkey2 equivalent might be: if ‘operator from’ WAS supported, and a dst type implemented ‘operator from’ and a src type implemented ‘operator to’, which would get used when converting from src type to dst type?

Left-sided vars have a bigger priority, I think…

If there’s something you can’t do this way, let me know and we can try to come up with a solution.

I’m triyng to do observable variables – sort of plain values wrapper which would notify listeners about value changing.

And I want to use this wrapper as a plain type, but I can’t catch value assignment without overriding of assign operator.

Variant type have a magic with value assigning – we can assign anything.

I want to do something like that but with strong types checking via generics.

My example:

Monkey

Namespace myapp Function Main() Local i1:=New Changable<Int>( 10 ) i1.Changed+=Lambda() Print "changed: "+i1 End i1=7 ' can't assign 'i1=i1+15 End Class Changable<T> Field Changed:Void() Method New() End Method New( value:T ) _value=value End Operator =( value:T ) 'trouble is here _value=value Changed() End Operator To:T() Return _value End Operator To:String() Return ""+_value End Property Value:T() Return _value End Private Field _value:T End

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Namespace myapp   Function Main()   Local i1:=New Changable<Int>( 10 ) i1.Changed+=Lambda() Print "changed: "+i1 End i1=7 ' can't assign 'i1=i1+15 End   Class Changable<T> Field Changed:Void() Method New() End Method New( value:T ) _value=value End Operator =( value:T ) 'trouble is here _value=value Changed() End Operator To:T() Return _value End Operator To:String() Return ""+_value End Property Value:T() Return _value End Private Field _value:T End

[Mark SiblyKeymaster]

No, I will not  supporting assignment overloading in the near future, if ever.

There are a lot of complications involved with assignment overloading which I’m not going to go into right now (email me if you want to discuss further…) but that I don’t want to weigh the language down with.

[nerobotParticipant]

No, I will not supporting assignment overloading in the near future, if ever.

I agree, and I never used it in c++.

Any ideas how to get what I want?

My idea is to have special base class with Assigned event. So we can’t break anything by overloading but can react on assignment:

Monkey

Class Assignable<T> Protected Field Assigned:Void( value:T ) ..... End

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Class Assignable<T>     Protected   Field Assigned:Void( value:T )   .....   End

Maybe this class will extends Variant but with generic type.

And usage:

Monkey

Class Changable<T> Extends Assignable<T> Field Changed:Void() Method New() Assigned=Lambda( value:T ) _value=value Changed() End End ......... End

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Class Changable<T> Extends Assignable<T> Field Changed:Void() Method New() Assigned=Lambda( value:T ) _value=value Changed() End End ......... End

[Mark SiblyKeymaster]

Any ideas how to get what I want?

I’m not actually sure what you want.

If you want a function to be called when a value is modified, you’ll need a ‘Set’ style method for assignments because, well, there is no assignment overloading. This is pretty trivial to implement though so I suspect you mean something else (or that you really *do* want assignment overloading!).

[nerobotParticipant]

If you want a function to be called when a value is modified, you’ll need a ‘Set’ style method for assignments

Yes, I want this! But don’t want to use Set or properties.:)

Saying about Class Assignable<T> above I meant to have it as a core type of monkey2 like a Variant is.

Variant have an assignment magic on a c++ side. I need right the same plus event Assigned to be able to react on value changes.

I know that this is very specific thing, but maybe it sounds useful not for me only.

[Mark SiblyKeymaster]

>Yes, I want this! But don’t want to use Set or properties.:)

So you do want assignment overloading…as I’ve said above, this is not happening sorry!

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