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casa::UnitVal Class Reference

describes any valid unit as a factor and a dimenion of SI units More...

#include <UnitVal.h>

List of all members.

Public Member Functions

 UnitVal ()
 Construct an non-dimensioned value of 1.
 UnitVal (const UnitVal &other)
 Copy constructor.
 UnitVal (Double factor)
 Construct an non-dimensioned value.
 UnitVal (Double factor, const String &s)
 Construct a fully dimensioned value.
 UnitVal (Double factor, Int pos)
 Construct a value with a single unit at position specified.
 ~UnitVal ()
 Destructor.
UnitValoperator= (const UnitVal &other)
 Assignment (copy semantics)
UnitVal pow (Int p)
 Raise a unit to an integer power.
UnitVal root (Int p) const
 Take integer root.
UnitVal sqrt () const
UnitValoperator*= (const UnitVal &other)
 Manipulate units.
UnitValoperator/= (const UnitVal &other)
 Divide different units.
Bool operator== (const UnitVal &other) const
 Compare the dimensionality of different units.
Bool operator!= (const UnitVal &other) const
const UnitDimgetDim () const
 Get the data parts of the unit value definition.
Double getFac () const
 Get the factor of the unit (as compared to pure SI units)

Static Public Member Functions

static Bool check (const String &s)
 Convert a unit string to a proper unit value and cache the result.
static Bool check (const String &s, UnitVal &loc)
 Convert a unit string to a proper unit value, cache the result and compare the dimension with the specified unit value.

Static Public Attributes

static UnitVal NODIM
 Some constants to check type of units.
static UnitVal UNDIM
static UnitVal LENGTH
static UnitVal MASS
static UnitVal TIME
static UnitVal CURRENT
static UnitVal TEMPERATURE
static UnitVal INTENSITY
static UnitVal MOLAR
static UnitVal ANGLE
static UnitVal SOLIDANGLE

Protected Member Functions

void init (Double factor)
 alternate initialization
void init (Double factor, Int pos)

Static Private Member Functions

static Bool create (const String &s, UnitVal &res)
 Convert (and check) a unit string to an SI value representation.
static Bool create (MUString &str, UnitVal &res)
static Int psign (MUString &str)
 Determine sign of unit power (i.e.
static Int power (MUString &str)
 Determine exponent of unit symbol.
static Bool field (MUString &str, UnitVal &res)
 Determine symbol name in unit string.

Private Attributes

Double kindFactor
 The factor necessary to express the specified unit in the defining SI units.
UnitDim kindDim
 The dimensions of the unit in the defining SI units.

Friends

class UnitVal_static_initializer
 ensure that statics are initialized
UnitVal operator* (const UnitVal &in, const UnitVal &other)
 Multiply.
UnitVal operator/ (const UnitVal &in, const UnitVal &other)
 Divide.
ostream & operator<< (ostream &os, const UnitVal &ku)
 Output a unit as a value and a string of SI defining units.

Detailed Description

describes any valid unit as a factor and a dimenion of SI units

Intended use:

Public interface

Review Status

Reviewed By:
UNKNOWN
Date Reviewed:
before2004/08/25
Test programs:
tUnit

Prerequisite

Etymology

The class name derives from Units and gives a Value for a unit string

Synopsis

Physical units are strings consisting of one or more names of known basic units, separated by '.' or ' ' (for multiplication) or '/' (for division). Each name can optionally be preceded by a standard decimal prefix, and/or followed by an (optionally signed) exponent. Example: km/s/(Mpc.s)2 is identical to km.s-1.Mpc-2.s-2

See the Unit class for more details.

The UnitVal class maps a Unit string to a factor and a dimension of SI defining units. E.g 'km/s' will be 1000 m.s-1 . This class is only of interest if the manipulation of units is of direct interest. Normally units will be used as Quantities and Quantums (see the Quantum class) only, i.e. as a physical quantity having a value and unit. The class can also be used to check the validity of a unit string.

Constructing UnitVal values

UnitVal has the following constructors:

Manipulating unit values

The UnitVal can be manipulated by the following operators and functions:

To aid in checking the dimensionality of units, the following constants are available:


Tip: Any other dimension can be checked by a combination; To check e;g; if a unit is an acceleration, use: UnitVal::LENGTH/UnitVal::TIME/UnitVal::TIME

Checking for valid unit strings

The validity of a unit string can be checked by:

    // Check if the given String is a valid unit representation. The String
    // will be cached in the unit maps for later reference if True
    if ( UnitVal::check( "km/s/Mpc") ) {...}

Example

An observation contains values in Janskys and in Westerbork Units. The data can be combined by the following code:

    // The Fits tape gave JY, we check if defined, else we define them
      if ( !UnitVal::check( "JY")) {
        UnitMap::putUser("JY", UnitVal(1.,"Jy"), "FITS way to write Jy");
      }
    // The Fits tape gave WU (which are defined):
    // We check if JY and WU are of the same dimension:
      if (UnitVal(1.,"JY") != UnitVal(1.,"WU")) {
        cerr << "Wrong dimension for either JY ( " << 
                UnitVal(1.,"JY")->getDim() <<
                ") or WU ( " <<
                UnitVal(1.,"WU")->getDim() << ")" << endl;
      }
    // And output the relation between WU and JY, and the WU value:
      cout << "1 WU = " << ( UnitVal(1.,"WU")/UnitVal(1.,"Jy") )->getVal() <<
             " JY with 1 WU = " << UnitVal(1.,"WU") << endl;

Motivation

To separate the actual manipulation of unit values from the related quantity

To Do

Definition at line 166 of file UnitVal.h.


Constructor & Destructor Documentation

Construct an non-dimensioned value of 1.

casa::UnitVal::UnitVal ( const UnitVal other)

Copy constructor.

casa::UnitVal::UnitVal ( Double  factor) [inline]

Construct an non-dimensioned value.

Definition at line 185 of file UnitVal.h.

References init().

casa::UnitVal::UnitVal ( Double  factor,
const String s 
)

Construct a fully dimensioned value.

Thrown Exceptions

casa::UnitVal::UnitVal ( Double  factor,
Int  pos 
) [inline]

Construct a value with a single unit at position specified.

Definition at line 194 of file UnitVal.h.

References init().

Destructor.


Member Function Documentation

static Bool casa::UnitVal::check ( const String s) [static]

Convert a unit string to a proper unit value and cache the result.

The function will return False if invalid string specified

static Bool casa::UnitVal::check ( const String s,
UnitVal loc 
) [static]

Convert a unit string to a proper unit value, cache the result and compare the dimension with the specified unit value.

False if any of the steps fails

static Bool casa::UnitVal::create ( const String s,
UnitVal res 
) [static, private]

Convert (and check) a unit string to an SI value representation.

static Bool casa::UnitVal::create ( MUString str,
UnitVal res 
) [static, private]
static Bool casa::UnitVal::field ( MUString str,
UnitVal res 
) [static, private]

Determine symbol name in unit string.

const UnitDim& casa::UnitVal::getDim ( ) const

Get the data parts of the unit value definition.

Get the dimensions in the defining SI units

Get the factor of the unit (as compared to pure SI units)

void casa::UnitVal::init ( Double  factor) [protected]

alternate initialization

Referenced by UnitVal().

void casa::UnitVal::init ( Double  factor,
Int  pos 
) [protected]
Bool casa::UnitVal::operator!= ( const UnitVal other) const
UnitVal& casa::UnitVal::operator*= ( const UnitVal other)

Manipulate units.

Multiply different units

UnitVal& casa::UnitVal::operator/= ( const UnitVal other)

Divide different units.

UnitVal& casa::UnitVal::operator= ( const UnitVal other)

Assignment (copy semantics)

Bool casa::UnitVal::operator== ( const UnitVal other) const

Compare the dimensionality of different units.

Raise a unit to an integer power.

static Int casa::UnitVal::power ( MUString str) [static, private]

Determine exponent of unit symbol.

static Int casa::UnitVal::psign ( MUString str) [static, private]

Determine sign of unit power (i.e.

if '.' or '/')

Take integer root.

Thrown Exceptions


Friends And Related Function Documentation

UnitVal operator* ( const UnitVal in,
const UnitVal other 
) [friend]

Multiply.

UnitVal operator/ ( const UnitVal in,
const UnitVal other 
) [friend]

Divide.

ostream& operator<< ( ostream &  os,
const UnitVal ku 
) [friend]

Output a unit as a value and a string of SI defining units.

friend class UnitVal_static_initializer [friend]

ensure that statics are initialized

Definition at line 175 of file UnitVal.h.


Member Data Documentation

Definition at line 263 of file UnitVal.h.

Definition at line 259 of file UnitVal.h.

Definition at line 261 of file UnitVal.h.

The dimensions of the unit in the defining SI units.

Definition at line 277 of file UnitVal.h.

The factor necessary to express the specified unit in the defining SI units.

Definition at line 274 of file UnitVal.h.

Definition at line 256 of file UnitVal.h.

Definition at line 257 of file UnitVal.h.

Definition at line 262 of file UnitVal.h.

Some constants to check type of units.

Definition at line 254 of file UnitVal.h.

Definition at line 264 of file UnitVal.h.

Definition at line 260 of file UnitVal.h.

Definition at line 258 of file UnitVal.h.

Definition at line 255 of file UnitVal.h.


The documentation for this class was generated from the following file: