干货调料批发市场:如何将float转换为string

如何将float转换为string

     可能有好多人，包括C语言老手都不知道如何将float数据转换为string，我就是这样，今天查了一下MSDN，才知道C提供了_gcvt函数实现这个功能，收获着实不小，为了方便自己查询，也为了那些像我这样的网友能够了解该函数的具体用法，我把MSDN的原文原封不动抄录如下：

_gcvt

Converts a floating-point value to a string, which it stores in a buffer.

char *_gcvt( double value , int digits , char * buffer );

Routine

Required Header

Compatibility

_gcvt

Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.

Libraries

LIBC.LIB

Single thread static library, retail version

LIBCMT.LIB

Multithread static library, retail version

MSVCRT.LIB

Import library for MSVCRT.DLL, retail version

Return Value

_gcvt returns a pointer to the string of digits. There is no error return.

Parameters

value

Value to be converted

digits

Number of significant digits stored

buffer

Storage location for result

Remarks

The _gcvt function converts a floating-point value to a character string (which includes a decimal point and a possible sign byte) and stores the string in buffer. The buffer should be large enough to accommodate the converted value plus a terminating null character, which is appended automatically. If a buffer size of digits + 1 is used, the function overwrites the end of the buffer. This is because the converted string includes a decimal point and can contain sign and exponent information. There is no provision for overflow. _gcvt attempts to produce digits digits in decimal format. If it cannot, it produces digits digits in exponential format. Trailing zeros may be suppressed in the conversion.

Example

                                                             /* _GCVT.C: This program converts -3.1415e5 * to its string representation. */#include #include void main( void ){   char buffer[50];   double source = -3.1415e5;   _gcvt( source, 7, buffer );   printf( "source: %f  buffer: '%s'\n", source, buffer );   _gcvt( source, 7, buffer );   printf( "source: %e  buffer: '%s'\n", source, buffer );}

Output

                                                             source: -314150.000000  buffer: '-314150.'source: -3.141500e+005  buffer: '-314150.'

长见识了，俺总是这样转化的：
char str[260];
float f = -3.1415926;
float f1 = 263e-5;
sprintf(str,"%f",f);
printf("%s\n",str);
sprintf(str,"%f",f1);
printf("%s\n",str);

#  Skyman 发表于2006-05-05 21:35:00  IP: 202.202.10.*

你这样做也行
但没有这样灵活
是吧？

#  zhnde 发表于2006-05-11 20:15:00  IP: 129.69.212.*

灵活吗？ 能具体解释一下吗？

#  Skyman 发表于2006-05-11 22:03:00  IP: 202.202.10.*

至少可以方便的控制有效数字的位数啊。

#  ztwaker 发表于2006-07-28 12:40:00  IP: 61.144.207.*

/*C++ impl*/
string cvt(const float fval)
{
stringstream ss;
ss << fval;
return ss.str();
}

......///

#  ztwaker 发表于2006-07-28 12:46:00  IP: 61.144.207.*

加上有效数字位数控制

string cvt(const float f, const int prec)
{
stringstream ss;
ss.precision(prec);
ss << f;
return ss.str();
}