QJsonObject insert QJsonValue(double) looses precision

[snoopy24]

Hi,

I have a double value which i want to bring into a QJsonObject. But on inserting the QJsonValue into the QJsonObject the precision of the value changed. But why

@
double x = 23.2;
QJsonObject obj;
QJsonValue v = QJsonValue(x);
obj.insert("value",v);

qDebug() << x;
qDebug() << v;
qDebug() << obj;

@

returns:

23.2
QJsonValue(double, 23.2)
QJsonObject({"value": 23.199999999999999})

What's going wrong here. Can anybody help me pls?

Thanks!

[JKSH]

Hi, and welcome to the Qt Dev Net!

There are two things you need to be aware of:

Your loss of precision occured when you assigned 23.2 to x. A

double, as defined by the "IEEE floating point standard":http://en.wikipedia.org/wiki/IEEE_floating_point, cannot store 23.2 precisely.

The different outputs you saw is due to "roundings" that qDebug() did before displaying the text. All 3 values are actually the same.

To check yourself, do this:
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qDebug() << obj;
qDebug() << obj.value("value");
qDebug() << obj.value("value").toDouble();
@