Plugin function "Round()" doesn't work properly

[pmk65]

Im working on a plugin and noticed that the calculations made differed from the ones I get from regular Javascript.
After a lot of debugging, I pinpointed the problem to the "Round()" function.

Here's an example of totally inconstant results (WeBuilder Plugin script):

Code: Select all

var test1 = Round(11.5); // Returns 12
var test2 = Round(10.5); // Returns 10 << SHOULD BE 11

Script.ClearMessages;
Script.Message(_t(test1));
Script.Message(_t(test2) + " WRONG! Should be 11");


Why does one number round UP but the other rounds DOWN, even if both have the exact same fraction (.5) ?

Program used: WeBuilder 2015 v13.2.0.164

[pmk65]

Turns out that Delphi/Webuilder uses a retarded form of rounding called "banker's rounding"!

Round y to an integer value, call it q.
If the fraction of y is 0.5, then q is the even integer nearest to y.

Here's a custom rounding function I made, that behaves as you expect a rounding function to work.

Code: Select all

   /**
    *
    * Helper function: Round float var to specific number of decimals
    *
    * @param     float   floatVar: The number to round
    * @param     int     decimalPlaces: Number of decimals
    * @return    float
    *
    */
   function RoundFloat(floatVar, decimalPlaces) {
      var p = StrToInt(Copy("1000000000", 1, decimalPlaces + 1)),
         t = floatVar * p,
         r = Trunc(t);
      if (Frac(t) >= 0.5) r = r + 1;
      return (r / p);
   }