GwySIUnit

GwySIUnit — SI unit representation, physical quantitiy formatting

Functions

#define	gwy_si_unit_duplicate()
#define	gwy_si_unit_assign()
GwySIUnit *	gwy_si_unit_new ()
GwySIUnit *	gwy_si_unit_new_parse ()
void	gwy_si_unit_set_from_string ()
void	gwy_si_unit_set_from_string_parse ()
gchar *	gwy_si_unit_get_string ()
GwySIUnit *	gwy_si_unit_multiply ()
GwySIUnit *	gwy_si_unit_divide ()
GwySIUnit *	gwy_si_unit_power ()
GwySIUnit *	gwy_si_unit_nth_root ()
GwySIUnit *	gwy_si_unit_power_multiply ()
GwySIUnit *	gwy_si_unit_factor_to_base ()
gboolean	gwy_si_unit_equal ()
gboolean	gwy_si_unit_equal_string ()
GwySIValueFormat *	gwy_si_unit_get_format ()
GwySIValueFormat *	gwy_si_unit_get_format_for_power10 ()
GwySIValueFormat *	gwy_si_unit_get_format_with_resolution ()
GwySIValueFormat *	gwy_si_unit_get_format_with_digits ()

Signals

void

value-changed

Run First

Types and Values

struct	GwySIUnit
struct	GwySIUnitClass

Object Hierarchy

    GObject
    ╰── GwySIUnit

Implemented Interfaces

GwySIUnit implements GwySerializable.

Includes

#include <libgwyddion/gwyddion.h>

Description

GwySIUnit object represents a physical SI unit (or any other unit), it can be created from a unit string with gwy_si_unit_new().

GwySIUnit is also responsible for prefixes selection and generally formatting of physical quantities (see also gwymath for pure number formatting functions). There are several functions computing value format (as a GwySIValueFormat structure) with given resolution -- gwy_si_unit_get_format_with_resolution(), or number of significant digits -- gwy_si_unit_get_format_with_digits().

Functions

gwy_si_unit_duplicate()

#define             gwy_si_unit_duplicate(siunit)

Convenience macro doing gwy_serializable_duplicate() with all the necessary typecasting.

Parameters

siunit

An SI unit to duplicate.

gwy_si_unit_assign()

#define             gwy_si_unit_assign(dest, source)

Convenience macro making one SI unit equal to another.

This is just a gwy_serializable_clone() wrapper with all the necessary typecasting.

Parameters

dest	Target SI unit.
source	Source SI unit.

Since: 2.51

gwy_si_unit_new ()

GwySIUnit *
gwy_si_unit_new (const gchar *unit_string);

Creates a new SI unit from string representation.

Unit string represents unit with no prefixes (e. g. "m", "N", "A", etc.)

Parameters

unit_string

Unit string (it can be NULL for an empty unit).

Returns

A new SI unit.

gwy_si_unit_new_parse ()

GwySIUnit *
gwy_si_unit_new_parse (const gchar *unit_string,
                       gint *power10);

Creates a new SI unit from string representation.

This is a more powerful version of gwy_si_unit_new(): unit_string may be a relatively complex unit, with prefixes, like "pA/s" or "km^2". Beside conversion to a base SI unit like "A/s" or "m^2" it also computes the power of 10 one has to multiply the base unit with to get an equivalent of unit_string .

For example, for "pA/s" it will store -12 to power10 because 1 pA/s is 1e-12 A/s, for "km^2" it will store 6 to power10 because 1 km^2 is 1e6 m^2.

Parameters

unit_string	Unit string (it can be NULL for an empty unit).
power10	Where power of 10 should be stored (or NULL).

Returns

A new SI unit.

gwy_si_unit_set_from_string ()

void
gwy_si_unit_set_from_string (GwySIUnit *siunit,
                             const gchar *unit_string);

Sets string that represents unit.

It must be base unit with no prefixes (e. g. "m", "N", "A", etc.).

Parameters

siunit	An SI unit.
unit_string	Unit string to set siunit from (it can be NULL for an empty unit).

gwy_si_unit_set_from_string_parse ()

void
gwy_si_unit_set_from_string_parse (GwySIUnit *siunit,
                                   const gchar *unit_string,
                                   gint *power10);

Changes an SI unit according to string representation.

This is a more powerful version of gwy_si_unit_set_from_string(), please see gwy_si_unit_new_parse() for some discussion.

Parameters

siunit	An SI unit.
unit_string	Unit string to set siunit from (it can be NULL for an empty unit).
power10	Where power of 10 should be stored (or NULL).

gwy_si_unit_get_string ()

gchar *
gwy_si_unit_get_string (GwySIUnit *siunit,
                        GwySIUnitFormatStyle style);

Obtains string representing a SI unit.

Parameters

siunit	An SI unit.
style	Unit format style.

Returns

A newly allocated string that represents the base unit (with no prefixes).

gwy_si_unit_multiply ()

GwySIUnit *
gwy_si_unit_multiply (GwySIUnit *siunit1,
                      GwySIUnit *siunit2,
                      GwySIUnit *result);

Multiplies two SI units.

Parameters

siunit1	An SI unit.
siunit2	An SI unit.
result	An SI unit to set to product of siunit1 and siunit2 . It is safe to pass one of siunit1 , siunit2 . It can be NULL too, a new SI unit is created then and returned.

Returns

When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later. Otherwise result itself is simply returned, its reference count is NOT increased.

gwy_si_unit_divide ()

GwySIUnit *
gwy_si_unit_divide (GwySIUnit *siunit1,
                    GwySIUnit *siunit2,
                    GwySIUnit *result);

Divides two SI units.

Parameters

siunit1	An SI unit.
siunit2	An SI unit.
result	An SI unit to set to quotient of siunit1 and siunit2 . It is safe to pass one of siunit1 , siunit2 . It can be NULL too, a new SI unit is created then and returned.

Returns

When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later. Otherwise result itself is simply returned, its reference count is NOT increased.

gwy_si_unit_power ()

GwySIUnit *
gwy_si_unit_power (GwySIUnit *siunit,
                   gint power,
                   GwySIUnit *result);

Computes a power of an SI unit.

Parameters

siunit	An SI unit.
power	Power to raise siunit to.
result	An SI unit to set to power of siunit . It is safe to pass siunit itself. It can be NULL too, a new SI unit is created then and returned.

Returns

When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later. Otherwise result itself is simply returned, its reference count is NOT increased.

gwy_si_unit_nth_root ()

GwySIUnit *
gwy_si_unit_nth_root (GwySIUnit *siunit,
                      gint ipower,
                      GwySIUnit *result);

Calulates n-th root of an SI unit.

This operation fails if the result would have fractional powers that are not representable by GwySIUnit.

Parameters

siunit	An SI unit.
ipower	The root to take: 2 means a quadratic root, 3 means cubic root, etc.
result	An SI unit to set to power of siunit . It is safe to pass siunit itself. It can be NULL too, a new SI unit is created then and returned.

Returns

On success: When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later, otherwise result itself is simply returned, its reference count is NOT increased. On failure NULL is always returned.

Since: 2.5

gwy_si_unit_power_multiply ()

GwySIUnit *
gwy_si_unit_power_multiply (GwySIUnit *siunit1,
                            gint power1,
                            GwySIUnit *siunit2,
                            gint power2,
                            GwySIUnit *result);

Computes the product of two SI units raised to arbitrary powers.

This is the most complex SI unit arithmetic function. It can be easily chained when more than two units are to be multiplied.

Parameters

siunit1	An SI unit.
power1	Power to raise siunit1 to.
siunit2	An SI unit.
power2	Power to raise siunit2 to.
result	An SI unit to set to siunit1 ^power1 *siunit2 ^power2 . It is safe to pass siunit1 or siunit2 . It can be NULL too, a new SI unit is created then and returned.

Returns

When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later. Otherwise result itself is simply returned, its reference count is NOT increased.

Since: 2.4

gwy_si_unit_factor_to_base ()

GwySIUnit *
gwy_si_unit_factor_to_base (GwySIUnit *siunit,
                            GwySIUnit *result,
                            gdouble *mfactor);

Factors a possibly derived SI unit to base units.

For instance, if siunit was set to "N/m" the result will be "kg/s^2".

Normally the result will consist only of the base seven SI units. However, recognised non-SI units (and pseudounits) in siunit , such as "px" are left intact in the decomposition.

Also note that the decomposition is done to prefixable units. Kilogram is not prefixable (gram is) and there is no general way to keep the kilo- on the kilograms when deriving units for different powers of 10. Therefore, the calculated factor corresponds to decomposition to grams.

You must multiply the corresponding data with factor if you intend to use the result for them instead of unit !

Parameters

siunit	An SI unit.
result	An SI unit to set to decomposed siunit . It is safe to pass siunit itself. It can be NULL too, a new SI unit is created then and returned.
mfactor	Location to store multiplicative factor between siunit and result . For instance, for electronvolt the value 1.60217653e-16 would be stored (the factor 1000 comes from kilogram). Pass NULL if you are only interested dimension equality.

Returns

When result is NULL, a newly created SI unit that has to be dereferenced when no longer used later. Otherwise result itself is simply returned, its reference count is NOT increased.

Since: 2.51

gwy_si_unit_equal ()

gboolean
gwy_si_unit_equal (GwySIUnit *siunit,
                   GwySIUnit *siunit2);

Checks whether two SI units are equal.

Parameters

siunit	First unit.
siunit2	Second unit.

Returns

TRUE if the units are equal.

gwy_si_unit_equal_string ()

gboolean
gwy_si_unit_equal_string (GwySIUnit *siunit,
                          const gchar *unit_string);

Checks whether an SI unit corresponds to given string.

Any power-of-ten prefixes are ignored. This function is mostly useful for quick commensurability checks with simple units such as "m" and for checking whether a unit is non-empty (by comparing with NULL or an empty string).

Parameters

siunit	An SI unit.
unit_string	Unit string (it can be NULL for an empty unit).

Returns

TRUE if the units is equivalent to the given string.

Since: 2.49

gwy_si_unit_get_format ()

GwySIValueFormat *
gwy_si_unit_get_format (GwySIUnit *siunit,
                        GwySIUnitFormatStyle style,
                        gdouble value,
                        GwySIValueFormat *format);

Finds a good format for representing a value.

The values should be then printed as value/format->magnitude [format->units ] with format->precision decimal places.

Parameters

siunit	An SI unit.
style	Unit format style.
value	Value the format should be suitable for.
format	A value format to set-up, may be NULL, a new value format is allocated then.

Returns

The value format. If format was NULL, a newly allocated format is returned, otherwise (modified) format itself is returned.

gwy_si_unit_get_format_for_power10 ()

GwySIValueFormat *
gwy_si_unit_get_format_for_power10 (GwySIUnit *siunit,
                                    GwySIUnitFormatStyle style,
                                    gint power10,
                                    GwySIValueFormat *format);

Finds format for representing a specific power-of-10 multiple of a unit.

The values should be then printed as value/format->magnitude [format->units ] with format->precision decimal places.

This function does not change the precision field of format .

Parameters

siunit	An SI unit.
style	Unit format style.
power10	Power of 10, in the same sense as gwy_si_unit_new_parse() returns it.
format	A value format to set-up, may be NULL, a new value format is allocated then.

Returns

The value format. If format was NULL, a newly allocated format is returned, otherwise (modified) format itself is returned.

gwy_si_unit_get_format_with_resolution ()

GwySIValueFormat *
gwy_si_unit_get_format_with_resolution
                               (GwySIUnit *siunit,
                                GwySIUnitFormatStyle style,
                                gdouble maximum,
                                gdouble resolution,
                                GwySIValueFormat *format);

Finds a good format for representing a range of values with given resolution.

The values should be then printed as value/format->magnitude [format->units ] with format->precision decimal places.

Parameters

siunit	An SI unit.
style	Unit format style.
maximum	The maximum value to be represented.
resolution	The smallest step (approximately) that should make a visible difference in the representation.
format	A value format to set-up, may be NULL, a new value format is allocated then.

Returns

The value format. If format was NULL, a newly allocated format is returned, otherwise (modified) format itself is returned.

gwy_si_unit_get_format_with_digits ()

GwySIValueFormat *
gwy_si_unit_get_format_with_digits (GwySIUnit *siunit,
                                    GwySIUnitFormatStyle style,
                                    gdouble maximum,
                                    gint sdigits,
                                    GwySIValueFormat *format);

Finds a good format for representing a values with given number of significant digits.

The values should be then printed as value/format->magnitude [format->units ] with format->precision decimal places.

Parameters

siunit	An SI unit.
style	Unit format style.
maximum	The maximum value to be represented.
sdigits	The number of significant digits the value should have.
format	A value format to set-up, may be NULL, a new value format is allocated then.

Returns

The value format. If format was NULL, a newly allocated format is returned, otherwise (modified) format itself is returned.

Types and Values

struct GwySIUnit

struct GwySIUnit;

The GwySIUnit struct contains private data only and should be accessed using the functions below.

struct GwySIUnitClass

struct GwySIUnitClass {
    GObjectClass parent_class;

    void (*value_changed)(GwySIUnit *siunit);
};

Signal Details

The “value-changed” signal

void
user_function (GwySIUnit *gwysiunit,
               gpointer   user_data)

The ::value-changed signal is emitted whenever SI unit changes.

Parameters

gwysiunit	The GwySIUnit which received the signal.
user_data	user data set when the signal handler was connected.

Flags: Run First