数学函数2.txt

一些用到的函数 功能齐全

   /* now turn the handle into a stream */ 
   stream = fdopen(handle, "w"); 

   if (stream == NULL) 
      printf("fdopen failed\n"); 
   else 
   { 
      fprintf(stream, "Hello world\n"); 
      fclose(stream); 
   } 
   return 0; 
} 
  
  

函数名: feof 
功  能: 检测流上的文件结束符 
用  法: int feof(FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   /* open a file for reading */ 
   stream = fopen("DUMMY.FIL", "r"); 

   /* read a character from the file */ 
   fgetc(stream); 

   /* check for EOF */ 
   if (feof(stream)) 
      printf("We have reached end-of-file\n"); 

   /* close the file */ 
   fclose(stream); 
   return 0; 
} 
  
  

函数名: ferror 
功  能: 检测流上的错误 
用  法: int ferror(FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   /* open a file for writing */ 
   stream = fopen("DUMMY.FIL", "w"); 

   /* force an error condition by attempting to read */ 
   (void) getc(stream); 

   if (ferror(stream))  /* test for an error on the stream */ 
   { 
      /* display an error message */ 
      printf("Error reading from DUMMY.FIL\n"); 

      /* reset the error and EOF indicators */ 
      clearerr(stream); 
   } 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fflush 
功  能: 清除一个流 
用  法: int fflush(FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 
#include <conio.h> 
#include <io.h> 

void flush(FILE *stream); 

int main(void) 
{ 
   FILE *stream; 
   char msg[] = "This is a test"; 

   /* create a file */ 
   stream = fopen("DUMMY.FIL", "w"); 

   /* write some data to the file */ 
   fwrite(msg, strlen(msg), 1, stream); 

   clrscr(); 
   printf("Press any key to flush\ 
   DUMMY.FIL:"); 
   getch(); 

   /* flush the data to DUMMY.FIL without\ 
      closing it */ 
   flush(stream); 

   printf("\nFile was flushed, Press any key\ 
   to quit:"); 
   getch(); 
   return 0; 
} 

void flush(FILE *stream) 
{ 
     int duphandle; 

     /* flush the stream's internal buffer */ 
     fflush(stream); 

     /* make a duplicate file handle */ 
     duphandle = dup(fileno(stream)); 

     /* close the duplicate handle to flush\ 
        the DOS buffer */ 
     close(duphandle); 
} 
  
  
  

函数名: fgetc 
功  能: 从流中读取字符 
用  法: int fgetc(FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   char ch; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* seek to the beginning of the file */ 
   fseek(stream, 0, SEEK_SET); 

   do 
   { 
      /* read a char from the file */ 
      ch = fgetc(stream); 

      /* display the character */ 
      putch(ch); 
   } while (ch != EOF); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fgetchar 
功  能: 从流中读取字符 
用  法: int fgetchar(void); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   char ch; 

   /* prompt the user for input */ 
   printf("Enter a character followed by \ 
   <Enter>: "); 

   /* read the character from stdin */ 
   ch = fgetchar(); 

   /* display what was read */ 
   printf("The character read is: '%c'\n", 
          ch); 
   return 0; 
} 
  
  
  

函数名: fgetpos 
功  能: 取得当前文件的句柄 
用  法: int fgetpos(FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   fpos_t filepos; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* report the file pointer position */ 
   fgetpos(stream, &filepos); 
   printf("The file pointer is at byte\ 
          %ld\n", filepos); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fgets 
功  能: 从流中读取一字符串 
用  法: char *fgets(char *string, int n, FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   char msg[20]; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* seek to the start of the file */ 
   fseek(stream, 0, SEEK_SET); 

   /* read a string from the file */ 
   fgets(msg, strlen(string)+1, stream); 

   /* display the string */ 
   printf("%s", msg); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: filelength 
功  能: 取文件长度字节数 
用  法: long filelength(int handle); 
程序例: 

#include <string.h> 
#include <stdio.h> 
#include <fcntl.h> 
#include <io.h> 

int main(void) 
{ 
   int handle; 
   char buf[11] = "0123456789"; 

   /* create a file containing 10 bytes */ 
   handle = open("DUMMY.FIL", O_CREAT); 
   write(handle, buf, strlen(buf)); 

   /* display the size of the file */ 
   printf("file length in bytes: %ld\n", 
   filelength(handle)); 

   /* close the file */ 
   close(handle); 
   return 0; 
} 
  
  

函数名: fillellipse 
功  能: 画出并填充一椭圆 
用  法: void far fillellipse(int x, int y, int xradius, int yradius); 
程序例: 

#include <graphics.h> 
#include <conio.h> 

int main(void) 
{ 
   int gdriver = DETECT, gmode; 
   int xcenter, ycenter, i; 

   initgraph(&gdriver,&gmode,""); 
   xcenter = getmaxx() / 2; 
   ycenter = getmaxy() / 2; 

   for (i=0; i<13; i++) 
   { 
      setfillstyle(i,WHITE); 
      fillellipse(xcenter,ycenter,100,50); 
      getch(); 
   } 

   closegraph(); 
   return 0; 
} 
  
  
  

函数名: fillpoly 
功  能: 画并填充一个多边形 
用  法: void far fillpoly(int numpoints, int far *polypoints); 
程序例: 

#include <graphics.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   /* request auto detection */ 
   int gdriver = DETECT, gmode, errorcode; 
   int i, maxx, maxy; 

   /* our polygon array */ 
   int poly[8]; 

   /* initialize graphics, local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* read result of initialization */ 
   errorcode = graphresult(); 
   if (errorcode != grOk) 
   /* an error occurred */ 
   { 
      printf("Graphics error: %s\n", 
             grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
      /* terminate with an error code */ 
   } 

   maxx = getmaxx(); 
   maxy = getmaxy(); 

   poly[0] = 20;        /* 1st vertext */ 
   poly[1] = maxy / 2; 

   poly[2] = maxx - 20; /* 2nd */ 
   poly[3] = 20; 

   poly[4] = maxx - 50; /* 3rd */ 
   poly[5] = maxy - 20; 

   /* 
      4th vertex. fillpoly automatically 
      closes the polygon. 
   */ 
   poly[6] = maxx / 2; 
   poly[7] = maxy / 2; 

   /* loop through the fill patterns */ 
   for (i=EMPTY_FILL; i<USER_FILL; i++) 
   { 
      /* set fill pattern */ 
      setfillstyle(i, getmaxcolor()); 

      /* draw a filled polygon */ 
      fillpoly(4, poly); 

      getch(); 
   } 

   /* clean up */ 
   closegraph(); 
   return 0; 
} 
  
  
  

函数名: findfirst, findnext 
功  能: 搜索磁盘目录; 取得下一个匹配的findfirst模式的文件 
用  法: int findfirst(char *pathname, struct ffblk *ffblk, int attrib); 
 int findnext(struct ffblk *ffblk); 
程序例: 

/* findnext example */ 

#include <stdio.h> 
#include <dir.h> 

int main(void) 
{ 
   struct ffblk ffblk; 
   int done; 
   printf("Directory listing of *.*\n"); 
   done = findfirst("*.*",&ffblk,0); 
   while (!done) 
   { 
      printf("  %s\n", ffblk.ff_name); 
      done = findnext(&ffblk); 
   } 

   return 0; 
} 
  
  
  

函数名: floodfill 
功  能: 填充一个有界区域 
用  法: void far floodfill(int x, int y, int border); 
程序例: 

#include <graphics.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   /* request auto detection */ 
   int gdriver = DETECT, gmode, errorcode; 
   int maxx, maxy; 

   /* initialize graphics, local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* read result of initialization */ 
   errorcode = graphresult(); 
   if (errorcode != grOk) 
   /* an error occurred */ 
   { 
      printf("Graphics error: %s\n", 
             grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
      /* terminate with an error code */ 
   } 

   maxx = getmaxx(); 
   maxy = getmaxy(); 

   /* select drawing color */ 
   setcolor(getmaxcolor()); 

   /* select fill color */ 
   setfillstyle(SOLID_FILL, getmaxcolor()); 

   /* draw a border around the screen */ 
   rectangle(0, 0, maxx, maxy); 

   /* draw some circles */ 
   circle(maxx / 3, maxy /2, 50); 
   circle(maxx / 2, 20, 100); 
   circle(maxx-20, maxy-50, 75); 
   circle(20, maxy-20, 25); 

   /* wait for a key */ 
   getch(); 

   /* fill in bounded region */ 
   floodfill(2, 2, getmaxcolor()); 

   /* clean up */ 
   getch(); 
   closegraph(); 
   return 0; 
} 
  
  
  

函数名: floor 
功  能: 向下舍入 
用  法: double floor(double x); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   double number = 123.54; 
   double down, up; 

   down = floor(number); 
   up = ceil(number); 

   printf("original number     %10.2lf\n", 
          number); 
   printf("number rounded down %10.2lf\n", 
          down); 
   printf("number rounded up   %10.2lf\n", 
          up); 

   return 0; 
} 
  
  
  

函数名: flushall 
功  能: 清除所有缓冲区 
用  法: int flushall(void); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   /* create a file */ 
   stream = fopen("DUMMY.FIL", "w"); 

   /* flush all open streams */ 
   printf("%d streams were flushed.\n", 
   flushall()); 

   /* close the file */ 
   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fmod 
功  能: 计算x对y的模, 即x/y的余数 
用  法: double fmod(double x, double y); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   double x = 5.0, y = 2.0; 
   double result; 

   result = fmod(x,y); 
   printf("The remainder of (%lf / %lf) is \ 
          %lf\n", x, y, result); 
   return 0; 
} 
  
  
  

函数名: fnmerge 
功  能: 建立新文件名 
用  法: void fnerge(char *path, char *drive, char *dir); 
程序例: 

#include <string.h> 
#include <stdio.h> 
#include <dir.h> 
  

int main(void) 
{ 
    char s[MAXPATH]; 
    char drive[MAXDRIVE]; 
    char dir[MAXDIR]; 
    char file[MAXFILE]; 
    char ext[MAXEXT];