[BUG-13231] Write values to a long datatype, gets wrong value

Ignition
1

Hi.

I’m having strange issues when writing big values to an tag of datatype long.

For example:
If I copy this value: 20190320140538866 into my tag through “Tag Browser” it will be ok.
If i write it from a script like this: system.tag.write(‘Workorder/Database/ProdPlanNumber’,20190320140538866)
then the tag will get another value: 20190320140538864

If i write 20190320140538867 the tag will get value 20190320140538868.

Running 7.9.10
Java 1.8.0_66

Best Regards, Mårten

2

Hmm. Must be coercion to double happening somewhere in Ignition after you pass the value to the scripting system.

3

Tried it in Ignition 8.0beta also it behaves the same there.

4

I made an issue to track this. At first glance this seems like a bug to me.

5

Hi.

I have made some more testing. if i’ll write a string value to an long (test-tag), the result is OK.
system.tag.write(‘Workorder/Database/test’,20190320140538497) -Gets wrong result (20190320140538496)
system.tag.write(‘Workorder/Database/test’,‘20190320140538497’) -Gets right result

So my workaround right now is to convert my long to a string:
system.tag.write(‘Workorder/Database/ProdPlanNumber’,str(call.getOutParamValue(“PlanNumber”)))

Just for information.

Best Regars, Mårten

6

Try using python's explicit long constant syntax:

system.tag.write(‘Workorder/Database/test’,20190320140538497L)
7

Tried it, but still gets 20190320140538496 instead

8

I guess somewhere in transit, either JSON or XML are used to encode data.

Those protocols typically encode a number as text.

These protocols by themselves have no hard limit on number size (see http://json.org/ as example), but libraries typically decode these as double-precision floating-point numbers. Since that’s the most generic number type.

9

Hmm. That’s a bug. You should contact support.

10

@Kevin.Herron already marked it as a bug and working on it I guess…

1 Like
11

Huh. I missed yesterday’s discussion somehow…