Why doesn't MOD return the correct value?

General
1

Why does this code not work

[code] dim d as new date

	MsgBox str( d.TotalSeconds mod 60 )  // Displays "-8" incorrectly[/code]

While this code does

[code] dim d as new date

	MsgBox str( 3569404548 mod 60 ) // Displays "48" correctly [/code]

Is there something funny about d.TotalSeconds being a double?

(Yes, I know you can use d.second but I’m more curious as to why the above fails.)

2

What if you use mod 60.0?

3

That’s because of d.TotalSecond is converted into Int32 before doing modulo operation. The conversion causes integer overflow. So, the result obviously would be wrong.

4

Try this

dim d as new Date
dim tsd as Double = d.TotalSeconds
dim tsu as UInt64 = tsd
dim tsi as Int64 = tsd
dim tsi32 as Int32 = tsd

MsgBox Str(tsd mod 60)
MsgBox Str(tsu mod 60)
MsgBox Str(tsi mod 60)
MsgBox Str(tsi32 mod 60)
5

This is exactly it. If you execute:

msgbox str(ctype(d.totalseconds, integer))

You’ll see the negative value due to the 32-bit integer overflow. But if you explicitly cast to int64 it will work.

MsgBox str( ctype(d.TotalSeconds, int64) mod 60 )
6

Interesting! Thank you everyone.