atof

This is a discussion on atof within the C++ Programming forums, part of the General Programming Boards category; Atof function returns 0 when there is some error during conversion AND when input string is "0", "0.0", ".0" or ...

  1. #1
    Registered User larry's Avatar
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    atof

    Atof function returns 0 when there is some error during conversion AND when input string is "0", "0.0", ".0" or whatever. That's what I understand form help. How can I know whether user really inputted zero or there was an error?
    Please excuse my poor english...

  2. #2
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    Lightbulb

    well, Im not sure, but atof might set errno to some value if an error occured. I'd check myself, but I recently had some computer trouble, and It would be just a lot of hassle. Try this



    Code:
    #include <stdio.h>
    #include <whatever header file atof is in>
    #include <iostream.h>  //I guess this is the C++ board, 
    // so i had better include this
    
    main()
    {
          int err = errno;
          atof( "aslfkhas;lf" );  // junk data to see if errno changes
          if( err != errno )
               cout << "atof sets errno on error!"
          else
               cout << "nope";
          return 0;
    }

  3. #3
    Guest Sebastiani's Avatar
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    Why not use strcmp() to test for it?



    if(atof(string) || !strcmp(string,"0")
    {
    /// Process good Data
    }
    else
    {
    /// print an error, set flag, etc.
    }


    Thus, typing "0" into the string will pass the "!strcmp(string,"0")"
    test whereas hitting "enter" or typing garbage (which passes the "atof(string)" test ) will not.
    Code:
    if( numeric_limits< byte >::digits != bits_per_byte )
        error( "program requires bits_per_byte-bit bytes" );
    24bbs.cpp

  4. #4
    Guest Sebastiani's Avatar
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    Why not use strcmp() to test for it?



    if(atof(string) > 0 || !strcmp(string,"0")
    {
    /// Process good Data
    }
    else
    {
    /// print an error, set flag, etc.
    }


    Thus, typing "0" into the string will pass the "!strcmp(string,"0")"
    test whereas hitting "enter" or typing garbage (which passes the "atof(string)" test ) will not.
    Code:
    if( numeric_limits< byte >::digits != bits_per_byte )
        error( "program requires bits_per_byte-bit bytes" );
    24bbs.cpp

  5. #5
    Registered User larry's Avatar
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    And what if user enters 0.0, 0e-0, .000 or something? I'd like this all to work, no restrictions in how he specifies zero.
    Please excuse my poor english...

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