how to convert string value into double format in c++

Question

How do I convert a string value into double format in C++?

possible duplicate of [How to parse a string to an int in C++?](http://stackoverflow.com/questions/194465/how-to-parse-a-string-to-an-int-in-c) — Björn Pollex, Nov 14 '10 at 15:05

score 10 · Answer 1 · answered Nov 14 '10 at 15:03

10

If you're using the boost libraries, lexical cast is a very slick way of going about it.

answered Nov 14 '10 at 15:03

Dave McClelland

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score 4 · Accepted Answer · answered Nov 14 '10 at 15:08

4

Use stringstream :

#include <sstream>

stringstream ss;
ss << "12.34";
double d = 0.0;
ss >> d;

answered Nov 14 '10 at 15:08

John Dibling

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score 2 · Answer 3 · answered Nov 14 '10 at 15:18

You can do with stringstream. You can also catch invalid inputs like giving non-digits and asking it to convert to int.

#include <iostream> 
#include <sstream>
using namespace std;

int main()
{
    stringstream s;
    string input;
    cout<<"Enter number: "<<endl;
    cin>>input;
    s.str(input);
    int i;
    if(s>>i)
        cout<<i<<endl;
    else
        cout<<"Invalid input: Couldn't convert to Int"<<endl;
}

If conversion fails, s>>i returns zero, hence it prints invalid input.

you seem to lack some spaces =) – Viktor Sehr Nov 14 '10 at 15:29 — Viktor Sehr, Nov 14 '10 at 15:29

how to convert string value into double format in c++

3 Answers3