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 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
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>
<example>
<srcblock>
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.
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.
Copy constructor (reference semantics)
Destructor, does nothing
Assignment (reference semantics)
Make a copy of the derived object (reference semantics).
Has the object really a mask?
Get the region used (always returns 0).
Returns False, as the LatticeExpr lattice is not writable.
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.
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.
Returns the shape of the Lattice including all degenerate axes (i.e. axes with a length of one)
Return the best cursor shape.
Returns the coordinates of the lattice expression.
Do the actual get of the data. The return value is always False, thus the buffer does not reference another array.
Do the actual get of the mask data. The return value is always False, thus the buffer does not reference another array.
An expression is not writable so this functions throws an exception.
Copy the data from this lattice to the given lattice.
Handle the Math operators (+=, -=, *=, /=). They work similarly to copyData(To). However, they are not defined for Bool types, thus specialized below.