converting double to string

This is a discussion on converting double to string within the C++ Programming forums, part of the General Programming Boards category; i wrote something to convert a string to a double, no probs there, but i cant reverse the process. i ...

  1. #1
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    converting double to string

    i wrote something to convert a string to a double, no probs there, but i cant reverse the process. i definitely need to be able to convert a double to a string, there is no way around it. any ideas on how to do it?

    i thought it might involve iterating through % operations, working from 10^0 through to 10^(number of digits) but im a little unsure of how this will work, plus there is the problem of a decimal point. i wont have to worry about doubles with exponents, so i guess that simplifies it a little

    any ideas?

  2. #2
    It's full of stars adrianxw's Avatar
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    sprintf()
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  3. #3
    _B-L-U-E_ Betazep's Avatar
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    write it to a file as a double. Read it as a char array. Put null character at the end. Lengthy... but effective.

    You could write one function to do this, and just call the function.

    *char convert (Type number);
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  4. #4
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    solution :)

    i got this tip from another board, but i thought id share it,

    #include <sstream>
    #include <string>

    ...

    double d = 10.427;
    double d2;
    std::string s;
    std::stringstream ss, ss2;

    ss << d; //put d into the stringstream
    ss >> s; //put this value into s

    //now s is a string holding "10.427"
    //Convert the other way. Use ss2 and d2.

    ss2 << s;
    ss2 >> d2;

    //d2 now holds 10.427, converted from the string s

    i had to play around with char* [] and stuff because i had a different implementation of string, but needless to say, it worked a charm, id also worked out another way, but this is much cleaner

    btw thanks for your help

  5. #5
    Confused Magos's Avatar
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    reply

    I'm not sure, but isn't there a function like dtoa()??? I know there is a itoa() that converts intergers to arrays (strings) (i to a = itoa).
    MagosX.com

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  6. #6
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    nope! itoa or ftoa are not standard functions... some compiler may provide them...

    the C++ way to do this conversation is strtream or stringstream

    the C way is sprintf()
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  7. #7
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    all double values have exp. you just dont see them.
    yeah, sprintf

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