Method of conversion between numbers and strings in C + + (recommended) _c language

1, the conversion between string numbers

(1) string--> char *
  string str ("OK");
  char * p = str.c_str ();

(2) char *-->string
  char *p = "OK";
  String str (p);

(3) char *-->cstring 
  char *p = "OK";
  CString m_str (p);
  or
  CString m_str;
  M_str.format ("%s", p);

(4) CString--> char *
  CString str ("OK");
  char * p = str. GetBuffer (0);
  ...
  Str. ReleaseBuffer ();

(5) String--> CString 
  cstring.format ("%s", String.c_str ()); 

(6) CString--> String
  string s (Cstring.getbuffer (0)); 
  GetBuffer () must be releasebuffer (), otherwise there is no free buffer space occupied, CString objects can not dynamically grow.

(7) double/float->cstring
  double data;
  Cstring.format ("%.2f", data); Retains 2 decimal places

(8) cstring->double
  CString s= "123.12";
  Double  D=atof (s);  
 
(9) String->double
 double D=atof (S.c_str ());

2. Digital spin string: Using the sprintf () function

Char str[10];
int a=1234321;
sprintf (str, "%d", a);
--------------------
Char str[10];
Double a=123.321;
sprintf (str, "%.3LF", a);
--------------------
Char str[10];
int a=175;
sprintf (str, "%x", a);//10 is converted to 16, if the output uppercase letter is sprintf (str,%x, a)
--------------------
char *itoa (int Value, char* string, int radix); 

You can also spin a number to a string, but itoa () is a platform-dependent (not a standard), so this function is not recommended here.

3. String number: Using the sscanf () function

Char str[]= "1234321";
int A;
SSCANF (str, "%d", &a);
.............
Char str[]= "123.321";
Double A;
SSCANF (str, "%LF", &a);
.............
Char str[]= "AF";
int A;
SSCANF (str, "%x", &a); 16-in-system conversion to 10-system

Alternatively, you can use Atoi (), Atol (), Atof ().

4, the use of StringStream class

Write a string with the Ostringstream object, similar to sprintf ()

 Ostringstream S1;
 int i =;
 S1 << "Hello" << i << Endl;
 String s2 = S1.str ();
 cout << S2;

Read a string with the Istringstream object, similar to SSCANF ()

 Istringstream stream1;
 string string1 = "n";
 STREAM1.STR (string1);
 int i;
 Stream1 >> i;
 cout << i << Endl; Displays 25

The above is a small series of C + + in the number and string between the conversion method (recommended) of the whole content, I hope to help you, a lot of support cloud Habitat Community ~