BaseEngine.h

Go to the documentation of this file.

// # BaseEngine.h: Base class for the TaQL UDF conversion engines
// # Copyright (C) 2018
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef MEAS_BASEENGINE_H
#define MEAS_BASEENGINE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/tables/TaQL/ExprNode.h>
#include <casacore/measures/TableMeasures/ScalarMeasColumn.h>
#include <casacore/measures/TableMeasures/ArrayMeasColumn.h>
#include <casacore/casa/Arrays/Array.h>
 
namespace casacore {
 
// <summary>
// Abstract base class for the TaQL UDF conversion engines
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="" date="" tests="tMeas.cc">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> EngineBase
// </prerequisite>
 
// <synopsis>
// DopplerEngine defines Engines (user defined functions) that can be used
// in TaQL to convert Measures for dopplers.
// In this way such derived values appear to be ordinary TaQL functions.
//
// Doppler conversions require a MeasFrame containing sky direction,
// epoch and position on earth.
// In TaQL these functions can be called like:
// <srcblock>
//   meas.rv ('TOPO', 1 'm/s', 'LSRK', 'CasA', date(),
//            [1e6m,1e6m,1e6m], 'WGS84')
// </srcblock>
// which converts the dopplers from LSRK to TOPO.
// <ul>
//  <li>
//  <src>toref</src> is a single constant string.
//  <li>
// <src>pos</src> can have various value types. A single numeric array is
// a series of RA,DEC in J2000. If given as a set, the last argument of the
// set can be the reference types of the values in the set. The values can
// be strings (indicating planetary objects) or value pairs giving lon,lat.
// The default reference type is J2000.
// </ul>
// All such functions return data with type double and unit Hz.
//
// Dopplers can be given like:
//    [v1,v2,...], fromRef
// where fromRef is the reference type.
//
// A doppler can also be a table column which usually knows its type.
// It can also be an expression (e.g. DOPPLER[0,]) which also knows the type.
// </synopsis>
 
// <motivation>
// It makes it possible to handle measures in TaQL.
// </motivation>
 
class BaseEngine {
 public:
  BaseEngine() : itsIsConst(False), itsNDim(-1) {}
 
  virtual ~BaseEngine();
 
  // Adapt the output shape and dimensionality for possible constant values.
  // It also sets the itsIsConst flag.
  // If the given shape is not empty the shape is set to it and an extra axis
  // is added if nvalues>0 (for e.g. LONLAT).
  // If nvalues=1, the first axis is removed from the shape.
  // Note that the shape might have been set to the column's shape if a
  // measure column is used.
  void adaptForConstant(const IPosition& shapeConstant, uInt nvalues = 0);
 
  // Extend the shape (if not empty) with the engine's shape.
  // If the engine is not const, itsIsConst is cleared.
  void extendBase(const BaseEngine&, Bool removeFirstAxis = False);
 
  // Get the output shape.
  const IPosition& shape() const { return itsShape; }
 
  // Get the output dimensionality.
  Int ndim() const { return itsNDim; }
 
  // Get the unit of the function's result.
  const Unit& unit() const { return itsOutUnit; }
 
  // Get the unit of the expression.
  const Unit& inUnit() const { return itsInUnit; }
 
  // Tell if the expression is constant.
  Bool isConstant() const { return itsIsConst; }
 
 protected:
  // Let a derived class derive its attributes.
  // The default implementation does nothing.
  virtual void deriveAttr(const Unit& unit, Int nval);
 
  // Let a derived class set its value type.
  // By default is does nothing.
  virtual void setValueType(Int valueType);
 
  // Let a derived class strip part of the reference type.
  // The default implementation returns the full type string.
  virtual String stripMeasType(const String& type);
 
  // # Data members.
  Bool itsIsConst;
  IPosition itsShape;
  Int itsNDim;  // <0 unknown shape, 0 scalar, >0 known shape
  Unit itsInUnit;
  Unit itsOutUnit;
  TableExprNode itsExprNode;
};
 
}  // namespace casacore
 
#endif