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LEL_module
lattices package (libcasa_lattices)

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## Topics

| LEL_module_internal_classes
| Internal LEL_module classes and functions.

## Classes

class | casacore::LatticeExpr< T >
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class | casacore::LatticeExprNode
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class | casacore::LELCoordinates
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## Detailed Description

Lattice expressions.

See below for an overview of the classes in this module.

### Prerequisite

- module Lattices

### Review Status

Reviewed By:
  Peter Barnes
Date Reviewed:
  1999/10/30

### Etymology

LEL: Lattice Expression Language.

### Synopsis

A LatticeExpr represents a mathematical expression of lattices. All standard operators, regions, and many, many functions can be used in an expression.
An expression is calculated on-the-fly. Thus only when the user gets a part of the lattice, is the expression calculated for that part. Subexpressions resulting in a scalar are calculated only once, on a get of the first part of the lattice expression.
Note that a lattice expression is not writable, thus using the put function on such a lattice results in an exception.
Note 223 gives a more detailed explanation of the capabilities of LEL (Lattice Expression Language).

If the expression consists of images, the result can also be treated as an image using class ImageExpr. With the command function in ImageExprParse it is possible to parse and execute a LEL expression given as as a string.