converting a string to an int or double..

This is a discussion on converting a string to an int or double.. within the C++ Programming forums, part of the General Programming Boards category; how would i go about converting a string to a double?...

  1. #1
    Waxy-Dock
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    Mar 2005
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    converting a string to an int or double..

    how would i go about converting a string to a double?

  2. #2
    Just Lurking Dave_Sinkula's Avatar
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    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  3. #3
    Registered User hk_mp5kpdw's Avatar
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    Northern Virginia/Washington DC Metropolitan Area
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    1. Use the atof function:
    Code:
    #include <iostream>
    #include <string>
    #include <cstdlib>
    
    using namespace std;
    
    int main()
    {
        string str("19.874");
        double d;
    
        // Use atof to convert string to double
        d = atof(str.c_str());
    
        // Output double value
        cout << d << endl;
    
        return 0;
    }
    2. Use stringstreams:
    Code:
    #include <iostream>
    #include <string>
    #include <sstream>
    
    using namespace std;
    
    int main()
    {
        string str("19.874");
        stringstream sstr(str);
        double d;
    
        // Extract double value from stringstream
        sstr >> d;
    
        // Output double value
        cout << d << endl;
    
        return 0;
    }
    I used to be an adventurer like you... then I took an arrow to the knee.

  4. #4
    essence of digital xddxogm3's Avatar
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    589
    http://www.cppreference.com/stdstring/atof.html

    this is how you can do it in C not C++ hope it helps

    [edit1]
    took me a little while to find the correct link.
    if you saw this with the old link, sorry to confuse you.

    here is the index to the site with good details
    http://www.cppreference.com/index.html

    if all else fails google it.
    [/edit1]
    Last edited by xviddivxoggmp3; 03-27-2005 at 01:14 PM.
    "Hence to fight and conquer in all your battles is not supreme excellence;
    supreme excellence consists in breaking the enemy's resistance without fighting."
    Art of War Sun Tzu

  5. #5
    Waxy-Dock
    Join Date
    Mar 2005
    Posts
    69
    thanks for that...

    also how do you convert a double to a string?

  6. #6
    Registered User
    Join Date
    Nov 2004
    Posts
    86
    using <sstream>:

    Code:
    #include <sstream>
     
    using namespace std;
     
    string makeString(double d)
    {
    	ostringstream ss;
    	ss<<d<<flush;
    	return ss.str(); 
    }
    Last edited by sean; 03-27-2005 at 05:30 PM. Reason: Improper Code Tag Use

  7. #7
    essence of digital xddxogm3's Avatar
    Join Date
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    Posts
    589
    here is another link i found that might be of assistance to you.
    all i did again was run a search on google to find it.
    it uses stringstream to convert from and to the formats your looking for.
    http://pegasus.rutgers.edu/~elflord/...ingstream.html
    "Hence to fight and conquer in all your battles is not supreme excellence;
    supreme excellence consists in breaking the enemy's resistance without fighting."
    Art of War Sun Tzu

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