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POCalling Matlab's MLApp.MLAppClass.FEval from F#
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2010-05-13T05:55:08.900
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2010-11-11T04:33:47.753
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Matlab provides a COM interface that supports remote execution of arbitrary functions (and code snippets). In particular, it has an Feval method that calls a given Matlab function. The third parameter to this method, pvarArgOut, has COM type VARIANT*, and appears in the Visual Studio F# editor as an argument of type: <pre><code>pvarArgOut: byref<obj> </code></pre> The following code calls interp1, which in Matlab returns a matrix (i.e. 2D double array) result, as is normal for most Matlab functions. <pre><code>let matlab = new MLApp.MLAppClass() let vector_to_array2d (v : vector) = Array2D.init v.Length 1 (fun i j -> v.[i]) let interp1 (xs : vector) (ys : vector) (xi : vector) = let yi : obj = new obj() matlab.Feval("interp1", 1, ref yi, vector_to_array2d xs, vector_to_array2d ys, vector_to_array2d xi) yi :?> float[,] </code></pre> This code compiles fine, but when calling interp1, I get a COM exception: <pre><code>A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll Additional information: Invalid callee. (Exception from HRESULT: 0x80020010 (DISP_E_BADCALLEE)) </code></pre> I get the same error whether initialize yi with a new obj, a new Array2D, or null. How does F# translate VARIANT output arguments? Update Here is the corrected version: <pre><code>let matlab = new MLApp.MLAppClass() let vector_to_array2d (v : vector) = Array2D.init v.Length 1 (fun i j -> v.[i]) let interp1 (xs : vector) (ys : vector) (xi : vector) = let mutable oi : obj = null matlab.Feval("interp1", 1, &oi, vector_to_array2d xs, vector_to_array2d ys, vector_to_array2d xi) (oi :?> obj[]).[0] :?> float[,] </code></pre>
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<com><matlab><f#><variant><comexception>
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Calling Matlab's MLApp.MLAppClass.FEval from F#
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1. PO
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1. USMatthew
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1. USMatthew
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