Abnormality

[doulostheou]

I came across something I don't understand. I think I could work around it, but I don't understand what is going on.

I create a function to round a given number to the nearest fifth:

Function RoundToFifth(dblNumber As Double) As Single
    Dim intNumber As Integer
    Dim dblRemainder As Double
    'To use this function with time: RoundToFifth((End-Start)*24)
    
    intNumber = Fix(dblNumber)
    dblRemainder = (dblNumber - Fix(dblNumber))
    
    dblRemainder = dblRemainder * 2
    dblRemainder = Round(dblRemainder, 1)
    dblRemainder = dblRemainder / 2
    
    RoundToFifth = intNumber + dblRemainder
End Function

I am using this function in a query to round the difference of two time values to the nearest fifth of an hour.

So, in the immediate window, I try the function out:
print roundtofifth((#3/10/05 3:05:56 PM#-#3/10/05 3:03:32 PM#)*24) produces .05. Works perfectly.

I put the same into my query, doing the calculation from the same two values stored in the table:
Test: RoundToFifth(([End]-[Start])*24) produces 0.0500000007450581 with the End and Start values being exactly the same.

I am going to add a round statement to the query to round to 2 decimals, as the value that is being produced in error is always off by a very minute amount. So that will solve my error, but I would really appreciate it if someone could explain what is happening.

 

[doulostheou]

I really appreciate the link. The article was very interesting. I have already replaced every instance of Round() in my code. I'm still not sure why I would get one result in the intermediate window and a different result in the query, but I do think I can safely chalk it up to the rounding errors discussed in the article.