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GLib Reference Manual | |
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Numerical DefinitionsNumerical Definitions — mathematical constants, and floating point decomposition |
#include <glib.h> #define G_IEEE754_FLOAT_BIAS #define G_IEEE754_DOUBLE_BIAS union GFloatIEEE754; union GDoubleIEEE754; #define G_E #define G_LN2 #define G_LN10 #define G_PI #define G_PI_2 #define G_PI_4 #define G_SQRT2 #define G_LOG_2_BASE_10
GLib offers mathematical constants such as G_PI for the value of pi; many platforms have these in the C library, but some don't, the GLib versions always exist.
The GFloatIEEE754 and GDoubleIEEE754 unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html
#define G_IEEE754_FLOAT_BIAS (127)
See http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html
#define G_IEEE754_DOUBLE_BIAS (1023)
See http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html
union _GFloatIEEE754
{
gfloat v_float;
struct {
guint mantissa : 23;
guint biased_exponent : 8;
guint sign : 1;
} mpn;
};
The GFloatIEEE754 and GDoubleIEEE754 unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html
union _GDoubleIEEE754
{
gdouble v_double;
struct {
guint mantissa_low : 32;
guint mantissa_high : 20;
guint biased_exponent : 11;
guint sign : 1;
} mpn;
};
The GFloatIEEE754 and GDoubleIEEE754 unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html
#define G_LN2 0.69314718055994530941723212145817656807550013436026
The natural logarithm of 2.
#define G_LN10 2.3025850929940456840179914546843642076011014886288
The natural logarithm of 10.
#define G_PI 3.1415926535897932384626433832795028841971693993751
The value of pi (ratio of circle's circumference to its diameter).
#define G_LOG_2_BASE_10 (0.30102999566398119521)
Used for fooling around with float formats, see http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html