libm (baremetal)

Baremetal 数学库实现，提供 C99 标准数学函数。适用于无操作系统的裸机环境，替代宿主系统的 libm。每个函数均提供 double 和 float（f 后缀）两个版本。

数学常量

宏	值	含义
M_E	2.71828...	e
M_LOG2E	1.44269...	log2(e)
M_LOG10E	0.43429...	log10(e)
M_LN2	0.69314...	ln(2)
M_LN10	2.30258...	ln(10)
M_PI	3.14159...	π
M_PI_2	1.57079...	π/2
M_PI_4	0.78539...	π/4
M_1_PI	0.31830...	1/π
M_2_PI	0.63661...	2/π
M_2_SQRTPI	1.12837...	2/√π
M_SQRT2	1.41421...	√2
M_SQRT1_2	0.70710...	1/√2

特殊值

宏	含义
NAN	非数值
INFINITY	正无穷
HUGE_VALF	float 正无穷
HUGE_VAL	double 正无穷
HUGE_VALL	long double 正无穷

浮点分类

宏	含义
fpclassify(x)	返回 FP_NAN/FP_INFINITE/FP_ZERO/FP_SUBNORMAL/FP_NORMAL
isinf(x)	是否为无穷
isnan(x)	是否为 NaN
isnormal(x)	是否为正常值
isfinite(x)	是否为有限值
signbit(x)	是否为负数

比较宏

宏	含义
isgreater(x, y)	x > y
isgreaterequal(x, y)	x >= y
isless(x, y)	x < y
islessequal(x, y)	x <= y
islessgreater(x, y)	x < y 或 x > y
isunordered(x, y)	任一为 NaN

三角函数

double acos(double);    float acosf(float);
double asin(double);    float asinf(float);
double atan(double);    float atanf(float);
double atan2(double, double);  float atan2f(float, float);
double cos(double);     float cosf(float);
double sin(double);     float sinf(float);
double tan(double);     float tanf(float);

双曲函数

double acosh(double);   float acoshf(float);
double asinh(double);   float asinhf(float);
double atanh(double);   float atanhf(float);
double cosh(double);    float coshf(float);
double sinh(double);    float sinhf(float);
double tanh(double);    float tanhf(float);

指数与对数

double exp(double);     float expf(float);
double exp2(double);    float exp2f(float);
double expm1(double);   float expm1f(float);
double log(double);     float logf(float);
double log10(double);   float log10f(float);
double log1p(double);   float log1pf(float);
double log2(double);    float log2f(float);

幂与根

double pow(double, double);  float powf(float, float);
double sqrt(double);    float sqrtf(float);
double cbrt(double);    float cbrtf(float);
double hypot(double, double);  float hypotf(float, float);

误差函数

double erf(double);     float erff(float);
double erfc(double);    float erfcf(float);

取整与余数

double ceil(double);    float ceilf(float);
double floor(double);   float floorf(float);
double rint(double);    float rintf(float);
double round(double);   float roundf(float);
double trunc(double);   float truncf(float);
double fmod(double, double);  float fmodf(float, float);
double modf(double, double *);  float modff(float, float *);

绝对值、最大值、最小值

double fabs(double);    float fabsf(float);
double fmax(double, double);  float fmaxf(float, float);
double fmin(double, double);  float fminf(float, float);
double fdim(double, double);  float fdimf(float, float);

浮点操作

double frexp(double, int *);  float frexpf(float, int *);
double ldexp(double, int);    float ldexpf(float, int);
double scalbn(double, int);   float scalbnf(float, int);
double scalbln(double, long); float scalblnf(float, long);