Conversion between double and string in C + +, char *

/** main.cpp * * Created on:apr 7 * author:lizhen*/#include<iostream>//#include "MySqrt.h"#include <math.h> #include <vector> #include <typeinfo>#include<exception>#include<stdexcept>#include<string.h>#include<sstream>#include<stdio.h>using namespacestd;classbase{ Public: Base () {cout<<"Create the base"<<Endl; }    Virtual~Base () {cout<<"destroy the base"<<Endl; }};classDerived: Publicbase{ Public: Derived () {cout<<"Derived is created"<<Endl; }    Virtual~Derived () {cout<<"Derived is destroying"<<Endl; }};//Double-->stringstringDoubleconvertostring (Doubled)    {Ostringstream OS; if(OS << D)returnOs.str (); return "Invalid conversion";}//string-->doubleDoubleStringconvertodouble (stringstr)    {istringstream iss (str); Doublex; if(ISS >> x)returnx; return 0.0;}//c-function double-->stringstringCfunctiondtos (Doubled) {    Charstr[ -]; sprintf (str,"%.3LF", D); returnstr;}//c-function string->doubleDoubleCfunctionstod (stringstr) {    DoubleDD; SSCANF (Str.c_str (),"%LF",&DD); returnDD;}intMain () {//string-->char*    stringStr"string"); Char*p = const_cast<Char*>(Str.c_str ()); cout<<"string->char*"<<p<<Endl; //char*-->string    Char*ch = const_cast<Char*> ("Char");//warning:deprecated Conversion from string constant to ' char* ' [-wwrite-strings]|    stringchstr (CH); cout<<"char *-->string"<<chstr<<Endl; //double&float--->string    DoubleDD =3.14; stringDdstr =doubleconvertostring (DD); cout<<ddstr<<Endl; //String--->double&float    stringSTRP ="3.5555555555"; DoubleStrdd =stringconvertodouble (STRP); cout<<strdd<<Endl; cout<<atof (Strp.c_str ()) <<Endl; //c-function double->string    stringSS = Cfunctiondtos (3.146789); cout<<"SS"<<ss<<Endl; //c-function string->string    DoubleCDD = Cfunctionstod ("3.14259"); cout<<cdd<<Endl;}

Run results

1 string-char*string2Char *--Stringchar3 3.14 4 3.55556 5 3.55556 6 SS3. 147 7 3.14259

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string-->char*

// string-->char*    string str ("string");     char *p = const_cast<char *>(Str.c_str ());    cout<<"string->char*"<<p<<endl;

Char*-->string

// char*-->string    char *ch = const_cast<char *> ("char"); // warning:deprecated Conversion from string constant to ' char* ' [-wwrite-strings]|    string chstr (CH);    cout<<"char *-->string"<<chstr<<endl;

===

Double/float-->string

String-->double/float

Using methods from the Sstream header file in C + +

= = outputs a double to a string using the Ostringstream output stream object

Here's how:

// Double-->string string doubleconvertostring (double  d) {    ostringstream os;     if return os.str ();     return " Invalid conversion " ;}

= = Use the Istringstream input stream object to place the contents of the string in a double variable

Methods are as follows

// string-->double double stringconvertodouble (string  str) {    istringstream iss (str);     Double   x;     if return x;     return 0.0 ;}

Using the methods in the Stdio.h header file in standard C

= = Use the sprintf (str, "%.3LF", dd) method to output the characters in a double variable to the string str

Here's how:

// c-function double-->string string cfunctiondtos (double  d) {    char str[];    sprintf (str,"%.3lf", D);     return str;}

= = Use the sscanf (str, "%d", &dd) method to place the contents of the string str in the double variable DD

Here's how:

// c-function string->double double cfunctionstod (string  str) {    double  DD;    SSCANF (Str.c_str (),"%lf",&dd);     return DD;}

Other methods

char *itoa (int value, char* string, int radix); int---->string
It is also possible to convert a number to a string, but itoa () is a platform-dependent (not standard) function, so it is not recommended here.

You can also use Atoi (), Atol (), Atof (). String can be--->int/double/float

Reference Documentation:

Http://www.cnblogs.com/luxiaoxun/archive/2012/08/03/2621803.html

Conversion between double and string in C + +, char *