C++——cmath

参考链接： C++ frexp()

写在前面 

这个库就是简单的整理一下吧，主要包含了各种常用数学函数。简要整理一下。目前只会整理一下自己遇到的函数，所有的函数用法可以参考：< cmath > (math.h)。 

头文件包含 

#include <math.h>  

Trigonometric functions 

1.cos 

/* cos example */

#include <stdio.h>      /* printf */

#include <math.h>       /* cos */

#define PI 3.14159265

int main ()

{

  double param, result;

  param = 60.0;

  result = cos ( param * PI / 180.0 );

  printf ("The cosine of %f degrees is %f.\n", param, result );

  return 0;

} 

Hyperbolic functions 

Exponential and logarithmic functions 

1.exp 

/* exp example */

#include <stdio.h>      /* printf */

#include <math.h>       /* exp */

int main ()

{

  double param, result;

  param = 5.0;

  result = exp (param);

  printf ("The exponential value of %f is %f.\n", param, result );

  return 0;

}

//Output:

//The exponential value of 5.000000 is 148.413159. 

2.frexp  将一个浮点数转换成0.5~1.0之间的数和2的整数指数。 

/* frexp example */

#include <stdio.h>      /* printf */

#include <math.h>       /* frexp */

int main ()

{

  double param, result;

  int n;

  param = 8.0;

  result = frexp (param , &n);

  printf ("%f = %f * 2^%d\n", param, result, n);

  return 0;

}

//Output:

//8.000000 = 0.500000 * 2^4 

3.ldexp  frexp函数逆运算，根据0.5~1.0之间的浮点数与n求出对应的浮点数。 

/* ldexp example */

#include <stdio.h>      /* printf */

#include <math.h>       /* ldexp */

int main ()

{

  double param, result;

  int n;

  param = 0.95;

  n = 4;

  result = ldexp (param , n);

  printf ("%f * 2^%d = %f\n", param, n, result);

  return 0;

}

//Output:

//0.950000 * 2^4 = 15.200000 

4.log  计算一个数的自然对数：log(x)，以e为底。 

/* log example */

#include <stdio.h>      /* printf */

#include <math.h>       /* log */

int main ()

{

  double param, result;

  param = 5.5;

  result = log (param);

  printf ("log(%f) = %f\n", param, result );

  return 0;

}

//Output:

//log(5.500000) = 1.704748 

5.log10  计算一个数的以10为底的对数：log10(x)。 

/* log10 example */

#include <stdio.h>      /* printf */

#include <math.h>       /* log10 */

int main ()

{

  double param, result;

  param = 1000.0;

  result = log10 (param);

  printf ("log10(%f) = %f\n", param, result );

  return 0;

}

//Output:

//log10(1000.000000) = 3.000000 

6.modf  将一个数分为整数与小数部分。 

/* modf example */

#include <stdio.h>      /* printf */

#include <math.h>       /* modf */

int main ()

{

  double param, fractpart, intpart;

  param = 3.14159265;

  fractpart = modf (param , &intpart);

  printf ("%f = %f + %f \n", param, intpart, fractpart);

  return 0;

}

//Output:

//3.141593 = 3.000000 + 0.14159 

7.exp2  求一个数为指数，2为底数的幂：2^x。 

/* exp2 example */

#include <stdio.h>      /* printf */

#include <math.h>       /* exp2 */

int main ()

{

  double param, result;

  param = 8.0;

  result = exp2 (param);

  printf ("2 ^ %f = %f.\n", param, result );

  return 0;

}

//Output:

//2 ^ 8.000000 is 256.000000. 

8.expm1  计算函数：e^x - 1的值。对于较小值的x，e^x - 1 比 exp(x) - 1更精确。 

/* expm1 example */

#include <stdio.h>      /* printf */

#include <math.h>       /* expm1 */

int main ()

{

  double param, result;

  param = 1.0;

  result = expm1 (param);

  printf ("expm1 (%f) = %f.\n", param, result );

  return 0;

}

//Output:

//expm1 (1.000000) = 1.718282. 

9.log2  计算以2为底的对数。 

/* log2 example */

#include <stdio.h>      /* printf */

#include <math.h>       /* log2 */

int main ()

{

  double param, result;

  param = 1024.0;

  result = log2 (param);

  printf ("log2 (%f) = %f.\n", param, result );

  return 0;

}

//Output:

//log2 (1024.000000) = 10.000000 

Power functions 

1.pow  计算乘积值。 

/* pow example */

#include <stdio.h>      /* printf */

#include <math.h>       /* pow */

int main ()

{

  printf ("7 ^ 3 = %f\n", pow (7.0, 3.0) );

  printf ("4.73 ^ 12 = %f\n", pow (4.73, 12.0) );

  printf ("32.01 ^ 1.54 = %f\n", pow (32.01, 1.54) );

  return 0;

}

//Output:

//7 ^ 3 = 343.000000

//4.73 ^ 12 = 125410439.217423

//32.01 ^ 1.54 = 208.036691 

2.sqrt 

/* sqrt example */

#include <stdio.h>      /* printf */

#include <math.h>       /* sqrt */

int main ()

{

  double param, result;

  param = 1024.0;

  result = sqrt (param);

  printf ("sqrt(%f) = %f\n", param, result );

  return 0;

}

//Output:

//sqrt(1024.000000) = 32.000000 

3.cbrt  计算一个数的立方根。 

/* cbrt example */

#include <stdio.h>      /* printf */

#include <math.h>       /* cbrt */

int main ()

{

  double param, result;

  param = 27.0;

  result = cbrt (param);

  printf ("cbrt (%f) = %f\n", param, result);

  return 0;

}

//Output:

//cbrt (27.000000) = 3.000000 

4.hypot  计算三角形的第三边。 

/* hypot example */

#include <stdio.h>      /* printf */

#include <math.h>       /* hypot */

int main ()

{

  double leg_x, leg_y, result;

  leg_x = 3;

  leg_y = 4;

  result = hypot (leg_x, leg_y);

  printf ("%f, %f and %f form a right-angled triangle.\n",leg_x,leg_y,result);

  return 0;

}

//Output:

//3.000000, 4.000000 and 5.000000 form a right-angled triangle. 

Error and gamma functions 

Rounding and remainder functions 

1.ceil  对一个小数向上取整数。 

/* ceil example */

#include <stdio.h>      /* printf */

#include <math.h>       /* ceil */

int main ()

{

  printf ( "ceil of 2.3 is %.1f\n", ceil(2.3) );

  printf ( "ceil of 3.8 is %.1f\n", ceil(3.8) );

  printf ( "ceil of -2.3 is %.1f\n", ceil(-2.3) );

  printf ( "ceil of -3.8 is %.1f\n", ceil(-3.8) );

  return 0;

}

//Output:

//ceil of 2.3 is 3.0

//ceil of 3.8 is 4.0

//ceil of -2.3 is -2.0

//ceil of -3.8 is -3.0 

2.floor  对一个小数向下取整数 

/* floor example */

#include <stdio.h>      /* printf */

#include <math.h>       /* floor */

int main ()

{

  printf ( "floor of 2.3 is %.1lf\n", floor (2.3) );

  printf ( "floor of 3.8 is %.1lf\n", floor (3.8) );

  printf ( "floor of -2.3 is %.1lf\n", floor (-2.3) );

  printf ( "floor of -3.8 is %.1lf\n", floor (-3.8) );

  return 0;

}

//Output:

//floor of 2.3 is 2.0

//floor of 3.8 is 3.0

//floor of -2.3 is -3.0

//floor of -3.8 is -4.0

Floating-point manipulation functions 

Minimum, maximum, difference functions 

Other functions 

1.fabs  浮点数取绝对值。 

/* fabs example */

#include <stdio.h>      /* printf */

#include <math.h>       /* fabs */

int main ()

{

  printf ("The absolute value of 3.1416 is %f\n", fabs (3.1416) );

  printf ("The absolute value of -10.6 is %f\n", fabs (-10.6) );

  return 0;

}

//Output:

//The absolute value of 3.1416 is 3.141600

//The absolute value of -10.6 is 10.600000 

2.abs  整数取绝对值。 

Classification macro / functions 

Comparison macro / functions 

Macro constants