<![CDATA[QJsonObject insert QJsonValue(double) looses precision]]>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!

]]>https://forum.qt.io/topic/37969/qjsonobject-insert-qjsonvalue-double-looses-precisionRSS for NodeSat, 05 Sep 2026 02:39:40 GMTTue, 18 Feb 2014 08:55:14 GMT60<![CDATA[Reply to QJsonObject insert QJsonValue(double) looses precision on Sat, 22 Feb 2014 04:46:22 GMT]]>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:
@
qDebug() << obj;
qDebug() << obj.value("value");
qDebug() << obj.value("value").toDouble();
@

]]>https://forum.qt.io/post/215813https://forum.qt.io/post/215813Sat, 22 Feb 2014 04:46:22 GMT