Bug? Unexpected result of initialising a Long value

B

Brian Dean

Well-Known Member

Licensed User

Longtime User

• Jul 13, 2025

• #1

B4X:

    Dim day1 As Long = 20193
    day1 = day1 * 24 * 3600 * 1000
    Log(DateTime.Date(day1))            ' Shows 04/15/2025
    Dim day2 As Long = 20193 * 24 * 3600 * 1000
    Log(DateTime.Date(day2))            ' Shows 01/11/1970

This might be a well-known behaviour but it took me a while to discover.

 

Cableguy

Expert

Licensed User

Longtime User

• Jul 13, 2025

• #2

In the first run, only day1 is long, and then you multiply them by INTs, on the second, you are defining the resulting operation of INTs as Long.... different things, give different results.
I would say it's a BUG, but ratter a "be careful with your definitions" heads up!

 

B

Brian Dean

Well-Known Member

Licensed User

Longtime User

• Jul 14, 2025

• #3

I am guessing that when you initialise a Long "in situ" it is initialised as an Int. Maybe there is a reason but it seems unexpected behaviour to me.

 

Erel

B4X founder

Staff member

Licensed User

Longtime User

• Jul 14, 2025

• #4

This is not a bug though it is a common pitfall.

The right hand side is evaluated and only then assigned to the long variable. As there are only ints on right side, the result is an int.
Another possible way to write it:

B4X:

Dim day2 As Long = (20193).As(Long) * 24 * 3600 * 1000