BUG: DATETIME Datatype Rounds Fractions of a Second

ID: Q139953

The information in this article applies to:

Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 5.0a, 6.0

SYMPTOMS

Repeatedly adding (or subtracting) a fraction of a second to (or from) a variable that contains a DATATIME data type results in an unexpected value being stored in the variable.

CAUSE

Visual FoxPro rounds the fraction of a second being added (or subtracted) up (or down) to the nearest whole second and stores the rounded value in the variable.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Steps to Reproduce Problem

1. Type the following line of code in the Command window:

   X = {1/1/95 12:00:00PM}

2. Type the following line of code in the Command window:

   Y = X + .1

3. Type the following line of code in the Command window:

   ? Y == X

The return value is True (.T.) even though you added a tenth of a second to x.

Another Demonstration of the Problem

1. Type the following line of code in the Command window:

   MODIFY COMMAND test

2. In the program window produced by the previous command, type the

   following lines of code:

   *---------------------
   *-- BEGIN PROGRAM TEST
   *---------------------
   CLEAR

   LOCAL X, Y
   X = {1/1/95 12:00:00pm}
   FOR I = 1 to 5

     *-- Show which iteration you are on
     DO CASE
          CASE I = 1
               WAIT WINDOW "Iteration 1" TIMEOUT .75
          CASE I = 2
               WAIT WINDOW "Iteration 2" TIMEOUT.75
          CASE I = 3
               WAIT WINDOW "Iteration 3" TIMEOUT.75
          CASE I = 4
               WAIT WINDOW "Iteration 4" TIMEOUT.75
          OTHERWISE
               WAIT WINDOW "Last Iteration" TIMEOUT.75
     ENDCASE

     *-- Add 1 tenth of a second to Y
     Y = X + .1

     *-- Display X
     WAIT WINDOW "X = " + TTOC(X) TIMEOUT 1

     *-- Compare Y and X
     *-- One would think the following comparison would return .F.
     WAIT WINDOW "Y == X is " + IIF(Y==X,".T.",".F.") + ;
          "  <<= First Test" + CHR(13) + ;
          "Y has been incremented" + CHR(13) + CHR(13) +;
          "Press any key to continue"

     *-- Add 1 tenth of a second to X
     X = X + .1

     *-- Compare Y and X
     *-- One would think the following comparison would return .T.
     WAIT WINDOW "Y == X is " + IIF(Y==X,".T.",".F.") + ;
          "  <<= Second Test" + CHR(13) + ;
          "X has been incremented" + CHR(13) + CHR(13) + ;
          "Press any key to continue"

     *-- Display Y
     WAIT WINDOW "Y = " + TTOC(Y) + ;
          CHR(13) + ;
          "Y has been incremented by .1 seconds" ;
          TIMEOUT 2
   ENDFOR
   *---------------------
   *-- END PROGRAM TEST
   *---------------------

3. Run the program. A one-second increase in time is displayed after five

   tenths of a second have accumulated. The incremented tenths are held by
   the variable but are never displayed until rounding the accumulated
   number of tenths results in a full second. Additionally, the comparison
   appears to be based on the rounding of the fractions of a second, not on
   the actual number stored to the variable.

KBCategory: kbprg kbbuglist KBSubcategory: FxprgGeneral vfoxwinbuglist5.00 buglist3.00 Additional reference words: 5.00 3.00 kbvfp300 kbvfp500 kbvfp600

Keywords          : kbprg kbVFp kbVFp500abug kbVFp500bug buglist3.00 FxprgGeneral kbbuglist
Version           : WINDOWS: 3.0,5.0,5.0a,6.0
Platform          : WINDOWS
Issue type        : kbbug