--- Log opened Sat Feb 25 00:00:14 2006
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06:19 < user317> how would i write .net bindings to a C library?
09:28 < user317> how do i convert a list into an array?
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09:58 <@nazgul`> [1,2,3].ToArray()
10:00 <@nazgul`> http://nemerle.org/PInvoke_(tutorial)
10:01 <@nazgul`> you can generally search for pinvoke on .NET and it should give you good results
10:10 < user317> it seems to work, except i have a function that returns an array of floats
10:10 < user317> and the value in mono is screwed up
10:14 <@nazgul`> hm, array[float] should work (I was using array[byte] in my app)
10:15 < user317> FANN_EXTERNAL fann_type* FANN_API fann_run(struct fann *ann, fann_type *input);  //fann_type is float
10:15 < user317> how would .net know the size of the array?
10:16 <@nazgul`> ok, so you should use  fann_type : ref float
10:17 <@nazgul`> as for structures, I don't have much experience with them, see http://www.mono-project.com/Interop_with_Native_Libraries
10:17 < user317> fann_run(fann : System.IntPtr, input : array[float]) : ref float;  ?
10:17 < user317> the intptr works fine
10:17 <@nazgul`> probably you will need to create a "copy" of struct definition in .NET
10:17 < user317> because i dont really care about its internals
10:18 <@nazgul`> fann_run(fann : System.IntPtr, input : ref float) : IntPtr    I would try this at first
10:18 <@nazgul`> IntPtr should be ok for any pointer type
10:18 < user317> how do I change it to a float array?
10:19 <@nazgul`> ah, if it is treated as buffer in C, then array[float] shoud be also ok :)
10:19 < user317> hehe
10:19 < user317> yea, it doesn't seem like it is
10:19 < user317> i get some random length array back with junk in it
10:20 <@nazgul`> hm, you mean the retrun value of "input" parameter?
10:20 < user317> i mean what i get back as the return of fann_run
10:20 < user317> input is fine
10:20 <@nazgul`> also, I wonder what FANN_EXTERNAL  and FANN_API is, maybe some macros?
10:21 < user317> i think they are just macros for static
10:21 < user317> a similar function that returns just a float from this library works fine
10:21 <@nazgul`> hm, I guess this is the problem, .NET can't know what should be the length of array
10:21 < user317> yea, thats what i think too
10:21 <@nazgul`> there probably is some way of specifying this...
10:21 < user317> but then at least the first part of the array should contain something that makes sense
10:22 <@nazgul`> but I don't know what :/
10:22 < user317> which it doesnt, its just junk
10:23 <@nazgul`> maybe you need IntPtr and then convert it manually
10:23 < user317> how would I do that?
10:23 <@nazgul`> specifying the length and using some Marshal magic 
10:24 <@nazgul`>    // convert native pointer to System::IntPtr with C-Style cast
10:25 <@nazgul`> Marshal::Copy((IntPtr)buf,byteArray, 0, len);
10:25 <@nazgul`> just found this :)
10:27 < user317> hmm
10:27 < user317> so i would pass hte return value int othat?
10:28 < user317> how do i get floats out of it
10:29 <@nazgul`> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemruntimeinteropservicesmarshalclasscopytopic.asp
10:29 <@nazgul`> but now you need to explicitly know the amount of elements you have there
10:30 < user317> i know that part
10:32 < user317> cool, i think this might work
10:32 <@nazgul`> so  def result = fann_run (...); def output = array (amount_of_returned); Marshal.Copy (result, output, 0, amount_of_returned);   output [0] == 0.0 :)
10:35 < user317> you are a genious
10:35 < user317> it worked perfectly
10:35 < user317> thanks a lot for your help
10:39 <@nazgul`> np :D
19:27 < user317> i need something that I can push and pop from both tail and head, is arraylist fast?
19:31 <@nazgul`> yes, I think manipulating end of arraylist is fast, the head should be also fast, though I'm not sure
19:32 <@nazgul`> this is implemented by a reallocated array, and push, pop operations are simply assign and move the current index (except the reallocation step)
19:34 < user317> ok, cool
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--- Log closed Sun Feb 26 00:00:16 2006