//=========================================================================================
/*virtual*/ Evaluator* Environment::CreateBinaryOperator( const char* operatorName, Evaluator* leftOperand, Evaluator* rightOperand, bool& isBinaryOperationEvaluator )
{
// Here we implement exponentiation in terms of Tayler series.
// This works for any type of number, because the Tyler series
// function only uses the arithmetic operations of the number interface.
// We re-write x^y as exp(y*ln x). The Tayler series are centered at zero.
// If the user does not want it centered at zero, they must call the
// Tyler series functions themselves. Environment derivatives, of course,
// can override this function to give the "^" operator a different meaning.
if( 0 == strcmp( operatorName, "^" ) )
{
Number* zero = CreateNumber();
zero->AssignAdditiveIdentity( *this );
FunctionArgumentEvaluator* argumentEvaluator = new FunctionArgumentEvaluator();
argumentEvaluator->Argument( leftOperand );
TaylorSeriesFunctionEvaluator* lnEvaluator = new TaylorSeriesFunctionEvaluator();
lnEvaluator->Center( zero, *this );
lnEvaluator->TaylorSeries( TaylorSeriesFunctionEvaluator::TAYLOR_SERIES_LN );
lnEvaluator->AddArgument( argumentEvaluator, FunctionEvaluator::APPEND_TO_LIST_OF_ARGS );
BinaryArithmeticOperationEvaluator* mulEvaluator = new BinaryArithmeticOperationEvaluator( BinaryArithmeticOperationEvaluator::ARITHMETIC_OPERATION_MULTIPLY );
mulEvaluator->LeftOperand( rightOperand );
mulEvaluator->RightOperand( lnEvaluator );
argumentEvaluator = new FunctionArgumentEvaluator();
argumentEvaluator->Argument( mulEvaluator );
TaylorSeriesFunctionEvaluator* expEvaluator = new TaylorSeriesFunctionEvaluator();
expEvaluator->Center( zero, *this );
expEvaluator->TaylorSeries( TaylorSeriesFunctionEvaluator::TAYLOR_SERIES_EXP );
expEvaluator->AddArgument( argumentEvaluator, FunctionEvaluator::APPEND_TO_LIST_OF_ARGS );
// We're not actually returning a binary operation evaluator.
isBinaryOperationEvaluator = false;
delete zero;
return expEvaluator;
}
return 0;
}
//=========================================================================================
/*virtual*/ bool EnvironmentInformationFunctionEvaluator::EvaluateResult( Number& result, Environment& environment )
{
result.AssignAdditiveIdentity( environment );
environment.PrintEnvironmentInfo();
return true;
}
