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Q258998: PRB: DateTime Subtraction May Not Produce an Exact Integer

Article: Q258998
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbvfp500 kbvfp500a kbvfp600 kbXBase kbGrpDSFox kbDSupport
Last Modified: 11-APR-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0 
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SYMPTOMS
========

When subtracting two DateTimes, the result is a floating point number. As such,
the displayed value may not be the exact value. This may lead to further
inaccuracies.

CAUSE
=====

Floating point math is frequently inaccurate in any language.

RESOLUTION
==========

When subtracting DateTimes, use ROUND(nDifference, 0) to ensure that you are
working with the value you think you are.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

To observe the problem, run the following code in the Command window:

  lnDiff = {^2000-03-20 11:31:00} - {^2000-03-20 10:25:00}
  ? lnDiff                      && 3960
  DISPLAY MEMORY LIKE lnDiff    && 3959.99996513
  ? INT(lnDiff)                 && 3960
  ? INT(lnDiff / 60)            && 65
  ? INT(ROUND(lnDiff, 0) / 60)  && 66

Additional query words:

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Keywords          : kbvfp500 kbvfp500a kbvfp600 kbXBase kbGrpDSFox kbDSupport 
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP600 kbVFP500a
Version           : WINDOWS:5.0,5.0a,6.0
Issue type        : kbprb
Solution Type     : kbnofix

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