Evaluate returns -1 for TRUE? (Why not 1)

user_4650297 0
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I was helping with another question, and I realized that using Evaluate in VBA seems to return -1 for TRUE statements.

Data:

Column A    Column B
A           A
A           B
C           C

So if I put =INT(A2=B2) and drag down, I get 1, 0, 1 which I expect.

However, using the following VBA, I get -1, 0, -1. 

For i = 2 To 4
    Cells(i, 4).Value = Evaluate(Int(Cells(i, 1) = Cells(i, 2)))
Next i

Why would EVALUATE use -1 for TRUE?

vba excel
1 Answers

VBA uses -1 for the True value. Cf. C and C++ which use 1.

-1 has all bits set to 1 in a 2’s complement signed integral type so the choice has some sense.

The choice goes way back to DOS BASIC (and other BASICs such as the one on the old BBC Micro) which predates the Component Object Model of the mid 1990s that’s still in use today.

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