Abstract base class for a user-defined TaQL function. More...

#include <UDFBase.h>

Public Types
typedef UDFBase *	MakeUDFObject (const String &functionName)
	The signature of a global or static member function creating an object of the UDF.
Public Member Functions
	UDFBase ()
	Only default constructor is needed.
virtual	~UDFBase ()
	Destructor.
virtual Bool	getBool (const TableExprId &id)
	Evaluate the function and return the result.
virtual Int64	getInt (const TableExprId &id)
virtual Double	getDouble (const TableExprId &id)
virtual DComplex	getDComplex (const TableExprId &id)
virtual String	getString (const TableExprId &id)
virtual TaqlRegex	getRegex (const TableExprId &id)
virtual MVTime	getDate (const TableExprId &id)
virtual Array< Bool >	getArrayBool (const TableExprId &id)
virtual Array< Int64 >	getArrayInt (const TableExprId &id)
virtual Array< Double >	getArrayDouble (const TableExprId &id)
virtual Array< DComplex >	getArrayDComplex (const TableExprId &id)
virtual Array< String >	getArrayString (const TableExprId &id)
virtual Array< MVTime >	getArrayDate (const TableExprId &id)
const String &	getUnit () const
	Get the unit.
void	init (const PtrBlock< TableExprNodeRep * > &arg, const Table &table, const TaQLStyle &)
	Initialize the function object.
TableExprNodeRep::NodeDataType	dataType () const
	Get the data type.
Int	ndim () const
	Get the dimensionality of the results.
const IPosition &	shape () const
	Get the result shape if the same for all results.
Bool	isConstant () const
	Tell if the UDF gives a constant result.
Static Public Member Functions
static void	registerUDF (const String &name, MakeUDFObject *func)
	Register a the name and construction function of a UDF (thread-safe).
static UDFBase *	createUDF (const String &name)
	Create a UDF object (thread-safe).
Protected Member Functions
PtrBlock< TableExprNodeRep * > &	operands ()
	Get the operands.
void	setDataType (TableExprNodeRep::NodeDataType)
	Set the data type.
void	setNDim (Int ndim)
	Set the dimensionality of the results.
void	setShape (const IPosition &shape)
	Set the shape of the results if it is fixed and known.
void	setUnit (const String &unit)
	Set the unit of the result.
void	setConstant (Bool isConstant)
	Define if the result is constant (e.g.
Private Member Functions
virtual void	setup (const Table &table, const TaQLStyle &)=0
	Set up the function object.
Private Attributes
PtrBlock< TableExprNodeRep * >	itsOperands
TableExprNodeRep::NodeDataType	itsDataType
Int	itsNDim
IPosition	itsShape
String	itsUnit
Bool	itsIsConstant
Static Private Attributes
static map< String, MakeUDFObject * >	theirRegistry
static Mutex	theirMutex

Detailed Description

Abstract base class for a user-defined TaQL function.

Synopsis

This class makes it possible to add user-defined functions (UDF) to TaQL. A UDF has to be implemented in a class derived from this class. A few functions have to be implemented in the class as described below.

A UDF is a class derived from this base class. It must contain the following member functions. See also the example below.

`makeObject`	a static function to create an object of the UDF class. This function needs to be registered.
`setup`	this virtual function is called after the object has been created. It should initialize the object using the function arguments that can be obtained using the function `operands()`. The setup function should perform the following: Define the data type of the result using `setDataType<src>. The data type should be derived from the data types of the function arguments. The possible data types are defined in class TableExprNodeRep. Note that a UDF can support multiple data types. For example, a function like <src>min` can be used for Int, Double, or a mix. Function 'checkDT' in class TableExprNodeMulti can be used to check the data types of the operands and determine the result data type. Define the dimensionality of the result using `setNDim`. A value of 0 means a scalar. A value of -1 means an array with a dimensionality that can vary from row to row. Optionally use `setShape` to define the shape if the results are arrays with a shape that is the same for all rows. It will also set ndim if setNDim was not used yet, otherwise it checks if it ndim matches. Optionally set the unit of the result using `setUnit`. TaQL has full support of units, so UDFs should behave the same. It is possible to change the unit of the function arguments. For example: a function like 'sin' can force its argument to be in radians; TaQL will scale the argument as needed. This can be done like `TableExprNodeUnit::adaptUnit (operands()[i], "rad");` A function like 'asin' will have a result in radians. Such a UDF should set its result unit to rad. A function like 'min' wants its arguments to have the same unit and will set its result unit to it. It can be done like: `setUnit (TableExprFuncNode::makeEqualUnits (operands(), 0, operands().size()));` Optionally define if the result is a constant value using `setConstant`. It means that the function is not dependent on the row number in the table being queried. This is usually the case if all UDF arguments are constant. See class TableExprFuncNode for more info about these functions.
`getXXX`	there are virtual get functions for each possible data type. The get functions matching the data types that can be set by the setup function need to be implemented.

A UDF has to be made known to TaQL by adding it to the UDF registry with its name and 'makeObject' function. UDFs will usually reside in a shared library that is loaded dynamically. TaQL will load a UDF in the following way:

The UDF name used in TaQL consists of two parts: a library name and function name separated by a dot. Both parts need to be given. Note that the library name can also be seen as a UDF scope, so different UDFs with equal names can be used from different libraries. A UDF should be registered with this full name.
If a UDF is not found in the registry, it will be tried to load a shared library using the library name part. The libraries tried to be loaded are lib<library>.so and libcasa_<library>.so. On Mac .dylib will be tried. If loaded successfully, a special function 'register_libname' will be called first. It should register each UDF in the shared library using UDFBase::register.

Example

      class TestUDF: public UDFBase
      {
      public:
        TestUDF() {}
        static UDFBase* makeObject (const String&)
          { return new TestUDF(); }
        virtual void setup (const Table&, const TaQLStyle&)
        {
          AlwaysAssert (operands().size() == 1, AipsError);
          AlwaysAssert (operands()[0]->dataType() == TableExprNodeRep::NTInt,
                        AipsError);
          AlwaysAssert (operands()[0]->valueType() == TableExprNodeRep::VTScalar,
                        AipsError);
          setDataType (TableExprNodeRep::NTBool);
          setNDim (0);                                 // scalar result
          setConstant (operands()[0].isConstant());    // constant result?
             
        }
        Bool getBool (const TableExprId& id)
          { return operands()[0]->getInt(id) == 1; }
      };

This example returns True if the function argument matches 1. It can be seen that it checks if the argument is an integer scalar.

Definition at line 163 of file UDFBase.h.

Member Typedef Documentation

typedef UDFBase* casa::UDFBase::MakeUDFObject(const String &functionName)

The signature of a global or static member function creating an object of the UDF.

Definition at line 168 of file UDFBase.h.

Constructor & Destructor Documentation

casa::UDFBase::UDFBase ( )

Only default constructor is needed.

virtual casa::UDFBase::~UDFBase ( ) [virtual]

Destructor.

Member Function Documentation

static UDFBase* casa::UDFBase::createUDF ( const String & name ) [static]

Create a UDF object (thread-safe).

TableExprNodeRep::NodeDataType casa::UDFBase::dataType ( ) const [inline]

Get the data type.

Definition at line 243 of file UDFBase.h.

References itsDataType.

virtual Array<Bool> casa::UDFBase::getArrayBool ( const TableExprId & id ) [virtual]

virtual Array<MVTime> casa::UDFBase::getArrayDate ( const TableExprId & id ) [virtual]

virtual Array<DComplex> casa::UDFBase::getArrayDComplex ( const TableExprId & id ) [virtual]

virtual Array<Double> casa::UDFBase::getArrayDouble ( const TableExprId & id ) [virtual]

virtual Array<Int64> casa::UDFBase::getArrayInt ( const TableExprId & id ) [virtual]

virtual Array<String> casa::UDFBase::getArrayString ( const TableExprId & id ) [virtual]

virtual Bool casa::UDFBase::getBool ( const TableExprId & id ) [virtual]

Evaluate the function and return the result.

Their default implementations throw a "not implemented" exception.

virtual MVTime casa::UDFBase::getDate ( const TableExprId & id ) [virtual]

virtual DComplex casa::UDFBase::getDComplex ( const TableExprId & id ) [virtual]

virtual Double casa::UDFBase::getDouble ( const TableExprId & id ) [virtual]

virtual Int64 casa::UDFBase::getInt ( const TableExprId & id ) [virtual]

virtual TaqlRegex casa::UDFBase::getRegex ( const TableExprId & id ) [virtual]

virtual String casa::UDFBase::getString ( const TableExprId & id ) [virtual]

const String& casa::UDFBase::getUnit ( ) const [inline]

Get the unit.

Definition at line 195 of file UDFBase.h.

References itsUnit.

void casa::UDFBase::init	(	const PtrBlock< TableExprNodeRep * > &	arg,
		const Table &	table,
		const TaQLStyle &
	)

Initialize the function object.

Bool casa::UDFBase::isConstant ( ) const [inline]

Tell if the UDF gives a constant result.

Definition at line 256 of file UDFBase.h.

References itsIsConstant.

Int casa::UDFBase::ndim ( ) const [inline]

Get the dimensionality of the results.

(0=scalar, -1=array with variable ndim, >0=array with fixed ndim

Definition at line 248 of file UDFBase.h.

References itsNDim.

PtrBlock<TableExprNodeRep*>& casa::UDFBase::operands ( ) [inline, protected]

Get the operands.

Definition at line 205 of file UDFBase.h.

References itsOperands.

static void casa::UDFBase::registerUDF	(	const String &	name,
		MakeUDFObject *	func
	)		`[static]`

Register a the name and construction function of a UDF (thread-safe).

An exception is thrown if this name already exists with a different construction function.

void casa::UDFBase::setConstant ( Bool isConstant ) [protected]

Define if the result is constant (e.g.

if all arguments are constant). If this function is not called by the setup function of the derived class, the result is not constant.

void casa::UDFBase::setDataType ( TableExprNodeRep::NodeDataType ) [protected]

Set the data type.

This function must be called by the setup function of the derived class.

void casa::UDFBase::setNDim ( Int ndim ) [protected]

Set the dimensionality of the results.

0 means that the results are scalars.
-1 means that the results are arrays with unknown dimensionality.
>0 means that the results are arrays with that dimensionality. This function must be called by the setup function of the derived class.

void casa::UDFBase::setShape ( const IPosition & shape ) [protected]

Set the shape of the results if it is fixed and known.

void casa::UDFBase::setUnit ( const String & unit ) [protected]

Set the unit of the result.

If this function is not called by the setup function of the derived class, the result has no unit.