unit_si.hh

Go to the documentation of this file.

/*
 * unit_si.hh
 *
 *  Created on: Aug 30, 2012
 *      Author: jb
 */


#ifndef UNIT_SI_HH_
#define UNIT_SI_HH_

#include <vector>
#include <string>


/**
 * @brief Class for representation SI units of Fields.
 *
 * Units are set through exponents of basic SI units. These exponents are set in methods with same
 * name as unit symbols (e.g. kg(), K() etc).
 *
 * Class contains method that provides formated string representing full unit symbol (usable in
 * LaTeX output).
 *
 * UnitSI object contains flag that says if it is defined
 * - undefined object can't be formated
 * - if any exponent is set, flag is set to defined
 *
 * Class contains static methods that return frequently used derived units (Watt, Pascal etc).
 */
class UnitSI {
public:
    /// Constructor
    UnitSI();

    /// Methods return frequently used derived units
    /// Returns Newton
    static UnitSI & N();
    /// Returns Joule
    static UnitSI & J();
    /// Returns Watt
    static UnitSI & W();
    /// Returns Pascal
    static UnitSI & Pa();
    /// Returns dimensionless unit
    static UnitSI & dimensionless();

    /// Methods set values of exponents for SI units with similar name
    UnitSI & m(int exp = 1);
    UnitSI & kg(int exp = 1);
    UnitSI & s(int exp = 1);
    UnitSI & A(int exp = 1);
    UnitSI & K(int exp = 1);
    UnitSI & mol(int exp = 1);
    UnitSI & cd(int exp = 1);
    /// Method sets value of exponent for m^{-d}, where d is dimension of region
    UnitSI & md(int exp = -1);

    /**
     * Makes unit description string in Latex format, e.g. "$[m.kg^{2}.s^{-2}]$"
     *
     * Have assert for undefined units.
     */
    std::string format() const;

    /**
     * Set flag that unit is undefined.
     *
     * Default value is true (set in constructor).
     * If any exponent is set, @p undef_ flag is unset.
     * In all fields unit must be defined by user.
     */
    void undef(bool val = true);

    /// Return true if the unit is defined.
    bool is_def() const;

private:
    /// Values determine positions of exponents in exponents_ vector
    enum UnitOrder {
        order_m=0,
        order_kg=1,
        order_s=2,
        order_A=3,
        order_K=4,
        order_mol=5,
        order_cd=6,
        order_md=7
    };

    /**
     * Stores exponents of base SI units in this order:
     * [m, kg, s, A, K, mol, cd, md]
     *
     * where md represents value of exponent depended on dimension (m^{-d})
     */
    std::vector<int> exponents_;

    /**
     * Flag if object is undefined.
     *
     * Value is set on true in constructor, when any exponent is changed, false value is set.
     */
    bool undef_;

    /// Product of two units.
    friend UnitSI operator *(const UnitSI &a, const UnitSI &b);
    /// Proportion of two units.
    friend UnitSI operator /(const UnitSI &a, const UnitSI &b);
};


/// Product of two units.
UnitSI operator *(const UnitSI &a, const UnitSI &b);

/// Proportion of two units.
UnitSI operator /(const UnitSI &a, const UnitSI &b);


#endif /* UNIT_SI_HH_ */