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RTableSelect - retrieve an element of an rtable in external code
RTableAssign - assign into an rtable in external code
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Calling Sequence
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RTableSelect(kv, rt, index)
RTableAssign(kv, rt, index, val)
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Parameters
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kv
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kernel handle of type MKernelVector
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rt
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type ALGEB rtable object
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index
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integer array denoting the element index
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val
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RTableData union value
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Description
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RTableSelect extracts the element at the index from the rtable rt. RTableAssign sets the element at the index in the rtable rt to val.
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These functions are especially useful for extracting elements from rtables with indexing functions or unusual storage. For example, assigning directly to the data-block of a dense symmetric Matrix may violate the symmetric property of the Matrix unless you are careful to ensure the element reflected along the diagonal is also updated. This is automatically handled when using RTableSelect and RTableAssign.
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The value val set by RTableAssign, and returned by RTableSelect is one of the datatypes in the RTableData union. The type must exactly correspond to the rtable data_type. The following union members match with these rtable_types.
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TYPE
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NAME
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DATA-TYPE
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INTEGER8
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int8
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RTABLE_INTEGER8
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INTEGER16
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int16
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RTABLE_INTEGER16
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INTEGER32
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int32
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RTABLE_INTEGER32
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INTEGER64
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int64
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RTABLE_INTEGER64
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FLOAT32
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float32
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RTABLE_FLOAT32
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FLOAT64
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float64
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RTABLE_FLOAT64
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ComplexFloat64
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complexf64
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RTABLE_COMPLEX
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CXDAG
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cxdag
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RTABLE_CXDAG
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ALGEB
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dag
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RTABLE_DAG
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Examples
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#include "maplec.h"
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ALGEB M_DECL MySwapRow( MKernelVector kv, ALGEB *args )
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{
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M_INT argc, i, index1[2], index2[2];
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RTableSettings rts;
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RTableData rtd1, rtd2;
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ALGEB rt;
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argc = MapleNumArgs(kv,(ALGEB)args);
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if( argc != 3 ) {
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MapleRaiseError(kv,"three argument expected");
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return( NULL );
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}
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rt = args[1];
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if( !IsMapleRTable(kv,rt) ) {
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MapleRaiseError(kv,"rtable expected");
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return( NULL );
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}
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RTableGetSettings(kv,&rts,rt);
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if( rts.num_dimensions != 2 ) {
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MapleRaiseError(kv,"2D rtable expected");
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return( NULL );
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}
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if( rts.read_only ) {
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MapleRaiseError(kv,"cannot modify read-only rtable");
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return( NULL );
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}
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index1[0] = MapleToM_INT(kv,args[2]);
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index2[0] = MapleToM_INT(kv,args[3]);
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for( i=RTableLowerBound(kv,rt,2); i<=RTableUpperBound(kv,rt,2); ++i ) {
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index1[1] = i;
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index2[1] = i;
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rtd1 = RTableSelect(kv,rt,index1);
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rtd2 = RTableSelect(kv,rt,index2);
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if( rts.data_type == RTABLE_INTEGER32 ) {
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MaplePrintf(kv,"Swapping rt[%d,%d] = %d and rt[%d,%d] = %dn",
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index1[0],index1[1],rtd1.int32,
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index2[0],index2[1],rtd2.int32 );
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}
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RTableAssign(kv,rt,index1,rtd2);
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RTableAssign(kv,rt,index2,rtd1);
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}
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return( rt );
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}
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Execute the external function from Maple.
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>
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>
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>
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>
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![Matrix([[1, 0, 2, 0], [0, 0, 0, 0], [0, 3, 0, 4], [0, 0, 0, 0]])](/support/helpjp/helpview.aspx?si=7975/file06279/math473.png)
| (1) |
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>
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![Matrix([[0, 3, 0, 4], [0, 0, 0, 0], [1, 0, 2, 0], [0, 0, 0, 0]])](/support/helpjp/helpview.aspx?si=7975/file06279/math480.png)
| (2) |
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![M := Matrix(4, 4, proc (i, j) options operator, arrow; i end proc, shape = symmetric, datatype = integer[4])](/support/helpjp/helpview.aspx?si=7975/file06279/math484.png)
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![M := Matrix([[1, 1, 1, 1], [1, 2, 2, 2], [1, 2, 3, 3], [1, 2, 3, 4]])](/support/helpjp/helpview.aspx?si=7975/file06279/math487.png)
| (3) |
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>
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Swapping rt[2,1] = 1 and rt[3,1] = 1
Swapping rt[2,2] = 2 and rt[3,2] = 2
Swapping rt[2,3] = 2 and rt[3,3] = 3
Swapping rt[2,4] = 2 and rt[3,4] = 3
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![Matrix([[1, 1, 1, 1], [1, 2, 3, 3], [1, 3, 2, 2], [1, 3, 2, 4]])](/support/helpjp/helpview.aspx?si=7975/file06279/math500.png)
| (4) |
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