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Thread: How to get exact value of double

  1. #1
    Join Date
    May 2017
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    Default How to get exact value of double

    How can one dump the exact value of a double variable to the console/terminal? I can do something like this:
    Qt Code:
    1. // var1 & var2 are both set elsewhere
    2. qDebug() << var1;
    3. qDebug() << var2;
    4. qDebug() << QString::number(var1,'f',4);
    5. qDebug() << QString::number(var2,'f',4);
    6. qDebug() << (var1 == var2);
    To copy to clipboard, switch view to plain text mode 

    This result will be:
    Qt Code:
    1. 0.05
    2. 0.05
    3. 0.0500
    4. 0.0500
    5. false
    To copy to clipboard, switch view to plain text mode 


    I have worked around these issues in the past with silly stuff like:
    Qt Code:
    1. var1 = (double)((int)((var1*100)+0.5))/100;
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    I'm not asking for the best workaround for rounding these numbers, merely what is the easiest way to dump the exact value of the variable, and not have it formatted via QT in some way?

  2. #2
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    Default Re: How to get exact value of double

    This thread from stackoverflow might help.

    Basically, you would use QString::number() as you have been, but replace the "4" with the value obtained from:

    Qt Code:
    1. std::numeric_limits< double >::max_digits10
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    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

  3. #3
    Join Date
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    Default Re: How to get exact value of double

    Thank you! Can't try it now, but this is right up to speed with what I was asking for.

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