Why does eval() script function introduce rounding errors?

Lar_123 · **Posted:** December 25th, 2007, 6:48 am

Better said, how do I fix that?

It seems that using the eval() has a limit of 6-digit accuracy. I found that it was rounding-up or rounding-down 8-digit numbers (Color values).

Any thoughts where to code a fix? A simple example script follows.

Quote:

numTEST01 = aStoredNumA ;
//
eval( "numTEST" + "02" +'='+ aStoredNumA ) ;

//
//
// Have a persistent Page variable storing 1589487571 as a number.
// have page variables numTEST01 and numTEST02 showing different results.
//
// this simple test reproduces the issue I am seeing. Showed up with an 8-digit integer.
//
// numTEST01 returns the value correctly 1589487571
//
// numTEST02 returns a rounded-UP number: 1589490000
//
//

Paul · **Posted:** December 26th, 2007, 7:11 pm

If the eval function contains a string, any number with 7 digits or more in it will be "rounded" incorrectly.

For example, a number alone:
foo = eval(1589487571);
Debug.trace(foo); // get 1589487571

Now add a string, even an empty one::

foo = eval(""+1589487571);
Debug.trace(foo); // get 1589490000

You get a similar effect if you apply toString to a number.

n = 1589487571;
foo = n.toString();
Debug.trace(foo); // get 1589490000

cheers
Paul

mackavi · **Posted:** December 27th, 2007, 7:02 pm

Wrong Eval syntax,

use

eval( "numTEST" + "02" +'= aStoredNumA' )

Happy holidays Lar

Paul · **Posted:** December 27th, 2007, 7:44 pm

Good one Mac,
I shouldn't post when I'm full of turkey, christmas pudding and wine.

cheers
Paul

Lar_123 · **Posted:** December 28th, 2007, 3:18 am

eval( "Thanks!" + 'Paul' +"and"+ 'Mac' ) ;

I really appreciate both the explanation and the fixes. I'm sure others will find this useful someday and will possibly keep them out of the deep end of trouble.

I am now getting into areas where I think I am using numbers or even boolean, only to find they're there as strings. So this small lesson in eval() illustrates one more potential hiccup.

Sure enough, Mac's syntax fix fixed this one in a snap.

Cheers.

Digital Workshop

Why does eval() script function introduce rounding errors?

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