casacore::LatticeExpr< T > Class Template Reference

Class to allow C++ expressions involving lattices. More...

#include <LatticeExpr.h>

Inheritance diagram for casacore::LatticeExpr< T >:

Public Member Functions
	LatticeExpr ()
	Default constructor.
	LatticeExpr (const LatticeExprNode &expr)
	Constructor from an arbitrary LatticeExprNode expression object.
	LatticeExpr (const LatticeExprNode &expr, const IPosition &latticeShape)
	LatticeExpr (const LatticeExpr< T > &other)
	Copy constructor (reference semantics).
virtual	~LatticeExpr ()
	Destructor, does nothing.
LatticeExpr< T > &	operator= (const LatticeExpr< T > &other)
	Assignment (reference semantics).
virtual MaskedLattice< T > *	cloneML () const
	Make a copy of the derived object (reference semantics).
virtual Bool	isMasked () const
	Has the object really a mask?
virtual const LatticeRegion *	getRegionPtr () const
	Get the region used (always returns 0).
virtual Bool	isWritable () const
	Returns False, as the LatticeExpr lattice is not writable.
virtual Bool	lock (FileLocker::LockType, uInt nattempts)
	Handle locking of the LatticeExpr which is delegated to all of its parts.
virtual void	unlock ()
virtual Bool	hasLock (FileLocker::LockType) const
virtual void	resync ()
	Resynchronize the Lattice object with the lattice file.
virtual IPosition	shape () const
	Returns the shape of the Lattice including all degenerate axes (i.e.
virtual IPosition	doNiceCursorShape (uInt maxPixels) const
	Return the best cursor shape.
virtual LELCoordinates	lelCoordinates () const
	Returns the coordinates of the lattice expression.
virtual Bool	doGetSlice (Array< T > &buffer, const Slicer &section)
	Do the actual get of the data.
virtual Bool	doGetMaskSlice (Array< Bool > &buffer, const Slicer &section)
	Do the actual get of the mask data.
virtual void	doPutSlice (const Array< T > &sourceBuffer, const IPosition &where, const IPosition &stride)
	An expression is not writable so this functions throws an exception.
virtual void	copyDataTo (Lattice< T > &to) const
	Copy the data from this lattice to the given lattice.
virtual void	handleMathTo (Lattice< T > &to, int oper) const
	Handle the Math operators (+=, -=, *=, /=).
template<>
void	handleMathTo (Lattice< Bool > &, int) const
Private Member Functions
void	init (const LatticeExprNode &expr)
	Initialize the object from the expression.
Private Attributes
LatticeExprNode	expr_p
IPosition	shape_p
LELArray< T > *	lastChunkPtr_p
Slicer	lastSlicer_p

Detailed Description

template<class T>
class casacore::LatticeExpr< T >

Class to allow C++ expressions involving lattices.

Intended use:

Public interface

Review Status

Date Reviewed:: yyyy/mm/dd

Prerequisite

Etymology

The name is derived from the fact that this class provides an expression interface to the user which s/he may use to write C++ expressions involving Lattices.

Synopsis

This class provides an interface which allows the C++ programmer to enter expressions such as "sin(a)+b" where "a" and "b" are Lattices.

This class is termed an envelope class, and inside it are the letter classes which do the real work. In reality, the letter classes are actually accessed via a bridging class called LatticeExprNode, which exists to handle type conversions. The letter classes iterate through the Lattices and evaluate the expression for each chunk of the iteration (usually a tile shape).

It is in the LatticeExprNode class that all the available expression operations are defined, so you should look there to see what functionality is available.

A description of the implementation details of these classes can be found in Note 216

Example

 ArrayLattice<Float>   f1(IPosition (2,nx,ny));
 ArrayLattice<Float>   f2(IPosition (2,nx,ny));
 f2.set(2.0);
 f1.copyData(2*f2+f2);

In this example, the values of the pixels in Lattice f1 are set to the values resulting from the expression "2*f2 + f2" I.e. the expression is evaluated for each pixel in the Lattices

Note that : 1) the Lattice::copyData function is expecting a Lattice argument. 2) LatticeExpr inherits from Lattice and therefore a LatticeExpr object is a valid argument object type 3) The expression in the copyData call is automatically converted to a LatticeExprNode by the constructors and operators in LatticeExprNode 4) The LatticeExprNode object so created is automatically converted to a LatticeExpr by casting functions in LatticeExprNode.

Example

 ArrayLattice<Float>   f1(IPosition (2,nx,ny));
 ArrayLattice<Float>   f2(IPosition (2,nx,ny));
 ArrayLattice<Double>  d(IPosition (2,nx,ny));
 ArrayLattice<Complex> c(IPosition (2,nx,ny));
 ArrayLattice<Bool>    b(IPosition (2,nx,ny));
 
 f2.set(1.0); d.set(2.0); c.set(Complex(2.0,3.0)); b.set(True);
 f1.copyData( (3.5*f2) + (cos(d)) - (10/min(d,f2)*(-abs(c))*ntrue(b)) - (C::pi) );

In this rather silly example, we fill Lattice "f1" with the result of the expression. The expression shows the use of constants, unary operations, binary operations, 1D and 2D functions. It also shows how mixed types can be handled. The output Lattice is a Float, whereas mixed into the expression are subexpressions involving Float, Double, Complex and Bool Lattices.

Motivation

The Lattice expression classes enable the C++ programmer much simpler handling of mathematical expressions involving lattices. In addition, these classes provide the infrastructure on top of which we can build an image calculator for Glish users

To Do

masks
regions

Definition at line 142 of file LatticeExpr.h.

Constructor & Destructor Documentation

template<class T>

casacore::LatticeExpr< T >::LatticeExpr ( )

Default constructor.

template<class T>

casacore::LatticeExpr< T >::LatticeExpr ( const LatticeExprNode & expr )

Constructor from an arbitrary LatticeExprNode expression object.

An exception is thrown if the expression data type cannot be converted to the template data type. The shape argument is mandatory if the expression has no shape. If the expression has a shape and if shape is given, it is checked if they are equal.

template<class T>

casacore::LatticeExpr< T >::LatticeExpr	(	const LatticeExprNode &	expr,
		const IPosition &	latticeShape
	)

template<class T>

casacore::LatticeExpr< T >::LatticeExpr ( const LatticeExpr< T > & other )

Copy constructor (reference semantics).

template<class T>

virtual casacore::LatticeExpr< T >::~LatticeExpr ( ) [virtual]

Destructor, does nothing.

Member Function Documentation

template<class T>

virtual MaskedLattice<T>* casacore::LatticeExpr< T >::cloneML ( ) const [virtual]

Make a copy of the derived object (reference semantics).

Implements casacore::MaskedLattice< T >.

template<class T>

virtual void casacore::LatticeExpr< T >::copyDataTo ( Lattice< T > & to ) const [virtual]

Copy the data from this lattice to the given lattice.

template<class T>

virtual Bool casacore::LatticeExpr< T >::doGetMaskSlice	(	Array< Bool > &	buffer,
		const Slicer &	section
	)			`[virtual]`

Do the actual get of the mask data.

The return value is always False, thus the buffer does not reference another array.

Reimplemented from casacore::MaskedLattice< T >.

template<class T>

virtual Bool casacore::LatticeExpr< T >::doGetSlice	(	Array< T > &	buffer,
		const Slicer &	section
	)			`[virtual]`

Do the actual get of the data.

The return value is always False, thus the buffer does not reference another array.

Implements casacore::Lattice< T >.

template<class T>

virtual IPosition casacore::LatticeExpr< T >::doNiceCursorShape ( uInt maxPixels ) const [virtual]

Return the best cursor shape.

Reimplemented from casacore::LatticeBase.

template<class T>

virtual void casacore::LatticeExpr< T >::doPutSlice	(	const Array< T > &	sourceBuffer,
		const IPosition &	where,
		const IPosition &	stride
	)			`[virtual]`

An expression is not writable so this functions throws an exception.

Implements casacore::Lattice< T >.

template<class T>

virtual const LatticeRegion* casacore::LatticeExpr< T >::getRegionPtr ( ) const [virtual]

Get the region used (always returns 0).

Implements casacore::MaskedLattice< T >.

template<>

void casacore::LatticeExpr< Bool >::handleMathTo	(	Lattice< Bool > &	,
		int
	)			const `[inline]`

Definition at line 245 of file LatticeExpr.h.

template<class T>

virtual void casacore::LatticeExpr< T >::handleMathTo	(	Lattice< T > &	to,
		int	oper
	)			const `[virtual]`

Handle the Math operators (+=, -=, *=, /=).

They work similarly to copyData(To). However, they are not defined for Bool types, thus specialized below.

template<class T>

virtual Bool casacore::LatticeExpr< T >::hasLock ( FileLocker::LockType ) const [virtual]

Reimplemented from casacore::LatticeBase.

template<class T>

void casacore::LatticeExpr< T >::init ( const LatticeExprNode & expr ) [private]

Initialize the object from the expression.

template<class T>

virtual Bool casacore::LatticeExpr< T >::isMasked ( ) const [virtual]

Has the object really a mask?

Reimplemented from casacore::MaskedLattice< T >.

template<class T>

virtual Bool casacore::LatticeExpr< T >::isWritable ( ) const [virtual]

Returns False, as the LatticeExpr lattice is not writable.

Reimplemented from casacore::LatticeBase.

template<class T>

virtual LELCoordinates casacore::LatticeExpr< T >::lelCoordinates ( ) const [virtual]

Returns the coordinates of the lattice expression.

Reimplemented from casacore::LatticeBase.

template<class T>

virtual Bool casacore::LatticeExpr< T >::lock	(	FileLocker::LockType	,
		uInt	nattempts
	)			`[virtual]`

Handle locking of the LatticeExpr which is delegated to all of its parts.

hasLock() is True if all parts of the expression return True.
It is strongly recommended to use class LatticeLocker to handle lattice locking. It also contains a more detailed explanation of the locking process.

Reimplemented from casacore::LatticeBase.

template<class T>

LatticeExpr<T>& casacore::LatticeExpr< T >::operator= ( const LatticeExpr< T > & other )

Assignment (reference semantics).

Reimplemented from casacore::MaskedLattice< T >.

template<class T>

virtual void casacore::LatticeExpr< T >::resync ( ) [virtual]

Resynchronize the Lattice object with the lattice file.

This function is only useful if no read-locking is used, ie. if the table lock option is UserNoReadLocking or AutoNoReadLocking. In that cases the table system does not acquire a read-lock, thus does not synchronize itself automatically.
By default the function does not do anything at all.

Reimplemented from casacore::LatticeBase.

template<class T>

virtual IPosition casacore::LatticeExpr< T >::shape ( ) const [virtual]

Returns the shape of the Lattice including all degenerate axes (i.e.

axes with a length of one)

Implements casacore::LatticeBase.

template<class T>

virtual void casacore::LatticeExpr< T >::unlock ( ) [virtual]

Reimplemented from casacore::LatticeBase.