[Qgis-user] Field calculator QGIS2.4 division error

[Nathan Woodrow]

Hey,

There is no left to right here, / is higher order then * so both these are
the same:

>> exp = QgsExpression('100.0 * 50 / 2')
>> exp2 = QgsExpression('50 / 2 * 100.0')
>> exp.evaluate(), exp2.evaluate()
(2500.0, 2500.0)

What you are seeing is the QGIS expression engine doing the multiply part
result first, which returns a float, then it will say "is the left side a
int AND the right side a int" if that comes back as NO then it does a float
operation.  Basically this means once one of the values in the equation is
a float the result will come out as float.

If you want to see the details on how this works you can find it here
https://github.com/qgis/QGIS/blob/master/src/core/qgsexpression.cpp#L2093

- Nathan


On Sat, Aug 23, 2014 at 8:22 PM, ralfwessels <gis at ralf-wessels.de> wrote:

> Hi
> intereseting, didn't know the left to right rule explained by Zoltan:
>
> Siki Zoltan wrote
> > 100.0 * "HC01_VC04"  /  "HC01_VC03" will give you the right result.
> > First the multiplication is evaluated (left to right rule),...
>
> Learning never stops!
> ralf
>
>
>
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