请教头文件问题……
不知道我的头文件找错没……应该是软件的安装路径里面的include文件夹里面吧……比如math.h头文件，我想问的是，这里面除了预编译和定义之类的就没其他内容了，也就是说，如果我引用其中的sqrt函数，为什么能帮我把平方根计算出来，好像这里面没有数据之间的计算操作啊……难道是在编译过程中完成的？
那么，如果我自己想定义一个函数比如max函数用来比较2个数的大小，当然函数很好写，然后我在自己添加一个头文件，把这个函数放在里面，以后直接包含这个头文件就可以使用max函数了，这样可以吗？
可是，我感觉我怎样也不可能写出像下面的头文件一样的代码……
所以，请教高手指点一二，小菜不甚感激……
比如，当我打开一个math.h的头文件后……
代码如下：
/* math.h
Definitions for the math floating point package.
Copyright (c) Borland International 1987,1988
All Rights Reserved.
*/
#if __STDC__
#define _Cdecl
#else
#define _Cdecl cdecl
#endif
#ifndef _MATH_H
#define _MATH_H 1
#define EDOM 33 /* Math argument */
#define ERANGE 34 /* Result too large */
#define HUGE_VAL _huge_dble
extern double _Cdecl _huge_dble;
int _Cdecl abs (int x);
double _Cdecl acos (double x);
double _Cdecl asin (double x);
double _Cdecl atan (double x);
double _Cdecl atan2 (double y, double x);
double _Cdecl atof (const char *s);
double _Cdecl ceil (double x);
double _Cdecl cos (double x);
double _Cdecl cosh (double x);
double _Cdecl exp (double x);
double _Cdecl fabs (double x);
double _Cdecl floor (double x);
double _Cdecl fmod (double x, double y);
double _Cdecl frexp (double x, int *exponent);
long _Cdecl labs (long x);
double _Cdecl ldexp (double x, int exponent);
double _Cdecl log (double x);
double _Cdecl log10 (double x);
double _Cdecl modf (double x, double *ipart);
double _Cdecl pow (double x, double y);
double _Cdecl sin (double x);
double _Cdecl sinh (double x);
double _Cdecl sqrt (double x);
double _Cdecl tan (double x);
double _Cdecl tanh (double x);
struct exception
{
int type;
char *name;
double arg1, arg2, retval;
};
int _Cdecl matherr (struct exception *e);
#if !__STDC__
double cdecl hypot (double x, double y);
double cdecl poly (double x, int degree, double coeffs []);
double cdecl pow10 (int p);
struct complex /* as used by "cabs" function */
{
double x, y;
};
#define cabs(z) (hypot ((z).x, (z).y))
/* The customary matherr() exception handler for maths functions is
not compatible with the x3j11 draft standard for C. _matherr() is
provided as a compromise.
*/
typedef enum
{
DOMAIN = 1, /* argument domain error -- log (-1) */
SING, /* argument singularity -- pow (0,-2)) */
OVERFLOW, /* overflow range error -- exp (1000) */
UNDERFLOW, /* underflow range error -- exp (-1000) */
TLOSS, /* total loss of significance -- sin(10e70) */
PLOSS, /* partial loss of signif. -- not used */
} _mexcep;
double _Cdecl _matherr (_mexcep why, char *fun, double *arg1p,
double *arg2p, double retval);
/* Constants rounded for 21 decimals. */
#define M_E 2.71828182845904523536
#define M_LOG2E 1.44269504088896340736
#define M_LOG10E 0.434294481903251827651
#define M_LN2 0.693147180559945309417
#define M_LN10 2.30258509299404568402
#define M_PI 3.14159265358979323846
#define M_PI_2 1.57079632679489661923
#define M_PI_4 0.785398163397448309116
#define M_1_PI 0.318309886183790671538
#define M_2_PI 0.636619772367581343076
#define M_1_SQRTPI 0.564189583547756286948
#define M_2_SQRTPI 1.12837916709551257390
#define M_SQRT2 1.41421356237309504880
#define M_SQRT_2 0.707106781186547524401
#endif /* __STDC__ */
#endif
