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ToMaplehfData - extract an encoded ALGEB from an hfdata structure
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Calling Sequence
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ToMaplehfData(kv, hf)
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Parameters
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kv
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kernel handle of type MKernelVector
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hf
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an hfdata structure
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Description
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The ToMaplehfData function returns a Maple object that has been encoded in an hfdata structure.
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•
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All hfdata structures returned by EvalhfDataProc represent real floating point values. Currently the only way to get a Maple object encoded in an hfdata structure is to encode it using MapleTohfData.
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Examples
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#include <math.h>
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#include "maplec.h"
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ALGEB MyNewtonData( MKernelVector kv, ALGEB *args )
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{
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M_INT i;
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FLOAT64 tolerance, newguess, res;
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hfdata guess[2];
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ALGEB f, fprime, x;
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if( 3 != MapleNumArgs(kv,(ALGEB)args) ) {
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MapleRaiseError(kv,"three arguments expected");
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return( NULL );
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}
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if( IsMapleProcedure(kv,args[1]) ) {
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f = args[1];
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}
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else {
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ALGEB indets;
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indets = EvalMapleProc(kv,ToMapleName(kv,"indets",TRUE),1,args[1]);
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if( !IsMapleSet(kv,indets) || MapleNumArgs(kv,indets) != 1 ) {
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MapleRaiseError(kv,"unable to find roots");
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return( NULL );
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}
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i = 1;
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f = EvalMapleProc(kv,ToMapleName(kv,"unapply",TRUE),2,args[1],
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MapleSelectIndexed(kv,indets,1,&i));
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if( !f || !IsMapleProcedure(kv,f) ) {
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MapleRaiseError(kv,"unable to convert first arg to a procedure");
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return( NULL );
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}
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}
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x = ToMapleName(kv,"x",FALSE);
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fprime = EvalMapleProc(kv,ToMapleName(kv,"unapply",TRUE),2,
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EvalMapleProc(kv,ToMapleName(kv,"diff",TRUE),2,
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ToMapleFunction(kv,f,1,x),x),x);
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if( !fprime || !IsMapleProcedure(kv,fprime) ) {
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MapleRaiseError(kv,"unable to compute derivative");
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return( NULL );
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}
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DoubleTohfData( kv, MapleEvalhf( kv, args[2] ), 0, guess+1 );
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tolerance = MapleEvalhf(kv,args[3]);
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res = 0.0;
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for( i=0; i<500; ++i ) {
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res = RealhfData( kv, EvalhfDataProc(kv,f,1,guess) );
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if( fabs( res ) <= tolerance )
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break;
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newguess = RealhfData( kv, guess[1] ) -
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res / RealhfData( kv, EvalhfDataProc(kv,fprime,1,guess) );
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DoubleTohfData( kv, newguess, 0, guess+1 );
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}
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if( i == 500 ) {
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MapleRaiseError(kv,"unable to find root after 500 iterations");
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return( NULL );
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}
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return( ToMapleFloat(kv, RealhfData( kv, guess[1] ) ) );
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}
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Execute the external function from Maple.
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