Understanding the "Allow Unrounded Floating Point Operations" option
The Microsoft manuals preach that all the compiler options in the Advanced Optimization dialog box are to be considered unsafe, in that they might lead to incorrect results (or just program crashes!). This is true for most of them, but often one of such options - namely, the "Allow Unrounded Floating Point Operations" - can deliver correct results and prevent you from inserting a bug in your application. Consider the following code:
Dim x As Double, y As Double, i As Integer
x = 10 ^ 18
y = x + 1 ' this can't be expressed with 64 bits
MsgBox (y = x) ' displays "True" (uncorrect)
Strictly speaking, the MsgBox should display False, because the X and Y variables shouldn't contain the same value. The problem is, they do contain exactly the same value, because the values 1E18 e 1E18+1 are represented with the same 64-bit floating point Double value.
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