Again dotNet help needed - How to deal with structs and call this (new) method?

[Gravey]

how are you creating the struct instance? the following code SHOULD work but i get a 'No constructor found which matched argument list: alglib.lbfgs+lbfgsstate' error trying to create the struct instance. dotnet.loadAssembly @"C:\lbfgs"
lbfgs = dotNetClass "alglib.lbfgs"
state = dotNetObject "alglib.lbfgs+lbfgsstate"
math = dotNetClass "AP.Math"

n = 3
m = 2
x = dotNetObject "System.Double[]" 3
x.SetValue (100 * math.RandomReal() - 50) 0
x.SetValue (100 * math.RandomReal() - 50) 1
x.SetValue (100 * math.RandomReal() - 50) 2

lbfgs.minlbfgs n m &x 0.0d0 0.0d0 0.0d0 0 &state
EDIT: edited the double array, copied the wrong thing...

EDIT 2: so i cheated and created a function in the assembly to return a new instance of the lbfgsstate struct... anyway now i'm at the same point as you are with a 'No method found which matched argument list' error... i'm guessing maxscript is having a hard time passing non standard data types by reference, ie. the lbfgsstate struct instance. At this point i'd suggest writing a small piece of C# to help you do what you need by avoiding passing the lbfgsstate struct instance by reference directly in mxs

[martinB]

how are you creating the struct instance?

Yes, that seems to be the problem. I can create a dotNetClass value for the struct using dnc = dotNetClass "alglib.lbfgs+lbfgsstate" but I don't now how to create an instance of it.

Thanks for the suggestion about adding some C# code. Problem with that is that I then need to do this over and over again for each new class I want to use, and cannot directly update to a new version as it gets released anymore. Right now I'd like to understand what I am doing wrong with dotNet and/or MAXScript, or whether this is (another) bug?

Any other comments?
-- MartinB

[biddle]

how are you creating the struct instance? the following code SHOULD work but i get a 'No constructor found which matched argument list: alglib.lbfgs+lbfgsstate' error trying to create the struct instance.

lbfgs.minlbfgs n m &x 0.0d0 0.0d0 0.0d0 0 &state


Looks like you are missing an argument.

lbfgs.minlbfgs takes 9, this code passes 8. There should be another int before the state.

...and Martin I don't know how to create a boxed version of a struct without resorting to come C#.

[martinB]

...and Martin I don't know how to create a boxed version of a struct without resorting to come C#.

OK, thanks anyway!

-- MartinB

[biddle]

...and Martin I don't know how to create a boxed version of a struct without resorting to some C#.Now I do!

Create 1 element array of them and then get the first element.

state = ((dotnetobject "alglib.lbfgs+lbfgsstate[]" 1).get 0)

[martinB]

Now I do!

Create 1 element array of them and then get the first element.

state = ((dotnetobject "alglib.lbfgs+lbfgsstate[]" 1).get 0)

=8-)
Wow! What on earth made you try that?!
Is there any logic in that I can create an array of the struct, but not the struct itself?

Another dotNet mystery solved thanks to you,
thanks very much indeed!

-- MartinB

[biddle]

It's one of those .NET performance gotchas that you always hear about: adding a struct to an array implicitly boxes it up so that can it be handled as an Object.

...only here it works in our favour!

[martinB]

It's one of those .NET performance gotchas that you always hear about: adding a struct to an array implicitly boxes it up so that can it be handled as an Object.

...only here it works in our favour!

Jeeeeeez. I assume http://www.vistadb.net/blog/post/2008/08/15/Class-v-Struct.aspx talks about what you just said?

I would NEVER have found that solution....

Thank you very much indeed, again!
-- MartinB

[Gravey]

Looks like you are missing an argument. ha you're right! no more errors when I put in the missing 0 before &state.

and great find with the struct-array-get-0 business!

[martinB]

Small update to this problem:

Larry Minton from Autodesk pointed out to me that the problem in this case is that the struct does not declare a constructor. And while all structs have a parameterless default constructor, it does not show up using Reflection (which is the mechanism MAXScript uses to connect to dotNet). So it sounds like the cause of this problem is a dotNet limitation?

There is a workaround, though, by using the 'CreateInstance' method of the 'Activator' dotNet class, to create an instance of the struct. So, in my case, that would be

activator = dotNetClass "activator"
dnc = dotNetClass "alglib.lbfgs+lbfgsstate"
structinstance = activator.createInstance dnc
-- MartinB

[biddle]

I'd never come across 'System.Activator'. What a find!

There are days when I am sure I'm learning the .NET framework in reverse. This is one of them.

Larry is The Man.

We live and learn.

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.