access the rtable data in external code - Maple Help

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RTableDataBlock - access the rtable data in external code

Calling Sequence

RTableDataBlock(kv, rt)

Parameters

kv

-

kernel handle returned by StartMaple

rt

-

Maple rtable object

Description

• 

These functions are part of the OpenMaple interface to Microsoft Visual Basic.

• 

The RTable*DataBlock family of functions return a 1-D copy of the data contained in rt. Modifying the returned data does not change the original rtable. The RTable*DataBlock function called must match the datatype of the rtable, which can be obtained from the data_type field of the RTableSettings structure returned by RTableGetSettings.

• 

The specific RTableDataBlock function returns the address of the actual memory used by Maple to store the rtable data.  This can be used to copy a changed data-block back and so update the rtable in Maple memory space.

• 

The DoubleRTableDataBlock command provides a way to get the data of a datatype=float[8] rtable in a native 2-D or 3-D Visual Basic format.  A 2-D array returned can then be indexed via 2-D A(i,j) indexing instead of computing the equivalent A((j-1)*m+i-1) index into a 1-D array. In this case (i,j) will match the Maple index, usually starting at (1,1), whereas RTableF64DataBlock will always be offset from (0).

• 

The data block of an rtable with an indexing function may not exactly match the way the data looks when viewed from Maple. For example, the data stored in position [1,1] of an rtable with a special indexing function may not correspond to the (0) element accessed from the rtable.

• 

An error is raised if an attempt is made to get the data block from a Maple-sparse rtable.

Examples

Public Sub MySumElems(ByVal kv As Long)

    Dim rts As RTableSettings

    Dim rt As Long

    Dim val As Double

    Dim i As Long

    ' original rtable

    rt = EvalMapleStatement(kv, "Matrix([[1,2,3],[4,5,6]],datatype=float[8]);")

    ' ensure float[8] datatype before choosing DataBlock function

    RTableGetSettings kv, rts, rt

    If rts.data_type = RTABLE_FLOAT64 Then

        n = RTableNumElements(kv, rt)

        ReDim data(0 To n - 1) As Double

        data = RTableF64DataBlock(kv, rt)

        ' sum all the elements in rt

        val = 0

        For i = 0 To n - 1

            val = val + data(i)

        Next i

        Write #1, "sum = ", val

    End If

End Sub

See Also

OpenMaple, OpenMaple/VB/API, OpenMaple/VB/Examples, rtable, trademarks


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