Source code for scuq.si

## \file si.py
#  \brief This file contains the predefined SI units.
#
#  It models SI base units
#  and SI alternate units. The alternate units have been formed as
#  product other alternate SI units where possible as described in
#  NIST 330.
#  \see "The International System of Units"; Barry N. Taylor; NIST 330 (2001)
#  \author <a href="http://thomas.reidemeister.org/" target="_blank">
#  Thomas Reidemeister</a>

## \namespace scuq::si
# \brief This namespace contains the SI-units.

## \defgroup si The Standard System of Units Module
#
#  This module contains the predefined SI units. It models SI base units
#  and SI alternate units. The alternate units have been formed as
#  product other alternate SI units where possible as described in
#  NIST 330.
#  \see "The International System of Units"; Barry N. Taylor; NIST 330 (2001)
# \author <a href="http://thomas.reidemeister.org/" target="_blank">
#  Thomas Reidemeister</a>
# \addtogroup si
# @{

# standard modules
import locale
import string
import sys

# local modules
import scuq.units as units
import scuq.qexceptions as qexceptions




class SIModel(units.PhysicalModel):
    """The interface for a physical model for SI units.

    The basic intend of this class is to provide an mapping between
    SI base units and physical dimensions.
    """



    def __init__(self):
        """Default constructor."""
        return None




    def get_dimension(self, unit):
        """Get the pysical dimension that corresponds to the given SI base unit.

        unit: The unit to check the dimension for parameter is no SI base unit.

        Returns: The corresponding physical dimension.
        """
        if unit == METER:
            return units.LENGTH
        if unit == KILOGRAM:
            return units.MASS
        if unit == SECOND:
            return units.TIME
        if unit == AMPERE:
            return units.CURRENT
        if unit == MOLE:
            return units.SUBSTANCE
        if unit == CANDELA:
            return units.LUMINOUS_INTENSITY
        if unit == KELVIN:
            return units.TEMPERATURE
        # This should not happen, since we assume that only SI
        # units are used.
        raise qexceptions.UnknownUnitException("The unit is no SI-unit ", unit)




# Check if unicode is enabled (i.e. if the symbols are shown correctly)
# language, encoding = locale.getdefaultlocale()
# if( string.lower( encoding ) != "utf-8" ):
#     sys.stderr.write( "You should use UTF-8 instead of "+encoding
#                       +" as encoding, or the "
#                       +"SI units won't display correctly\n" )

# Change the default model for the Quantities.units module to
# the physical model of SI units
_model = SIModel()
units.set_default_model(_model)

## Unit instance to model the BaseUnit Ampere.
AMPERE = units.BaseUnit("A")
## Unit instance to model the BaseUnit Candela.
CANDELA = units.BaseUnit("cd")
## Unit instance to model the BaseUnit Kelvin.
KELVIN = units.BaseUnit("K")
## Unit instance to model the BaseUnit Kilogram.
KILOGRAM = units.BaseUnit("kg")
## Unit instance to model the BaseUnit Meter.
METER = units.BaseUnit("m")
## Unit instance to model the BaseUnit Mol.
MOLE = units.BaseUnit("mol")
## Unit instance to model the BaseUnit Second.
SECOND = units.BaseUnit("s")

# SI derived units.
# These units are modelled as product of the base unit and
# other alternate SI units. They do have a different symbol.

## Unit instance to model the SI unit Radian.
# \attention Because this library keeps only the canonical form
#            of the product of base units the Radian is compatible
#            to the neutral 1. Therefore its system unit is modelled
#            as "1" not as \f$\frac{m}{m}\f$.
RADIAN = units.AlternateUnit("rad", units.ONE)

## Unit instance to model the SI base unit Steradian.
# \attention Because this library keeps only the canonical form
#            of the product of base units the Radian is compatible to
#            the neutral 1. Therefore its system unit is modelled
#            as "1" not as \f$\frac{m^2}{m^2}\f$.
STERADIAN = units.AlternateUnit("sr", units.ONE)

## Unit instance to model the SI unit Herz.
HERTZ = units.AlternateUnit("Hz", ~SECOND)

## Unit instance to model the SI unit Newton.
NEWTON = units.AlternateUnit("N", KILOGRAM * METER / (SECOND**2))

## Unit instance to model the SI unit Pascal.
PASCAL = units.AlternateUnit("Pa", NEWTON / (METER**2))

## Unit instance to model the SI unit Joule.
JOULE = units.AlternateUnit("J", NEWTON * METER)

## Unit instance to model the SI unit Watt.
WATT = units.AlternateUnit("W", JOULE / SECOND)

## Unit instance to model the SI unit Coulomb.
COULOMB = units.AlternateUnit("C", AMPERE * SECOND)

## Unit instance to model the SI unit Volt.
VOLT = units.AlternateUnit("V", WATT / AMPERE)

## Unit instance to model the SI unit Farad.
FARAD = units.AlternateUnit("F", COULOMB / VOLT)

## Unit instance to model the SI unit Ohm.
# \note The <tt>UTF-8</tt> encoded string stands for \f$\Omega\f$.  HGK: changed to Ohm
OHM = units.AlternateUnit(
    'u"\N{GREEK CAPITAL LETTER OMEGA}"',  # ( u"\u03A9" ).encode( "UTF-8" ),
    VOLT / AMPERE,
)

## Unit instance to model the SI unit Siemens.
SIEMENS = units.AlternateUnit("S", AMPERE / VOLT)

## Unit instance to model the SI unit Weber.
WEBER = units.AlternateUnit("Wb", VOLT * SECOND)

## Unit instance to model the SI unit Tesla.
TESLA = units.AlternateUnit("T", WEBER / (METER**2))

## Unit instance to model the SI unit Henry.
HENRY = units.AlternateUnit("H", WEBER / AMPERE)

## Unit instance to model the SI unit degree Celsius.
CELSIUS = KELVIN + 273.15

## Unit instance to model the SI unit Lumen.
LUMEN = units.AlternateUnit("lm", CANDELA * STERADIAN)

## Unit instance to model the SI unit Lux.
LUX = units.AlternateUnit("lx", LUMEN / (METER * METER))

## Unit instance to model the SI unit Becquerel.
BECQUEREL = units.AlternateUnit("Bq", ~SECOND)

## Unit instance to model the SI unit Gray.
GRAY = units.AlternateUnit("Gy", JOULE / KILOGRAM)

## Unit instance to model the SI unit Sivert.
SIVERT = units.AlternateUnit("Sv", JOULE / KILOGRAM)

## Unit instance to model the SI unit Katal.
KATAL = units.AlternateUnit("kat", MOLE / SECOND)


## @}