Double & Single

[Arc]

Can someone explain these 2 variable types to me please. integers & longs i understand but these 2 i'm not sure about.

I dim dbDub as Double and i set its value to 111,111,111,111,111 and it = 111billion,111million,111thousond,111. But when i add 1 more 1 it all of a sudden = 1.11111111111111E+15.

Now what does this mean? does it mean i now have 1.1 as a value or do i have 1 trillion,111billion,etc....

What is the difference in speed as compared to Longs and Integers?

Would i only use Doubles and Singles when i need to use decimal places?

Thanks!

[rjlohan]

Double is to Single as Long is to Integer.

Double and Single are both floating-point variables. The double can hold numbers twice as big. If you make them sufficiently large, they start displaying in scientific notation, and I think you may lose a small amount of accuracy.

[vbgladiator]

I believe

1.11111111111111E+15.


means
1.11111111111111 * 10^15

[rjlohan]

That's scientific notation alright...

[riis]

If you would like some technical information about this, click here. But be warned, it's quite complex

Double precision floats have an accuracy of 15 decimals, so if you have larger numbers (or if you have more than 15 decimals, before and after the comma), doubles will never exactly hold the value you intended to.
Single precision floats only have an accuracy of 7 decimals. In most cases this is sufficient.

Calculations with longs and ints are pretty much faster. So, if you're introducing a floating point value, consider if you really need it. Many times the usage of a float can be simulated by multiplying with another integer number. (For example money: $0.15 is also equal to 15 cents.)

If you have any more questions, just ask them. Good luck

[Arc]

Thaks alot riis for the tutorial and explination.. It helped alot.

[beachbum]

Originally posted by riis
Double precision floats have an accuracy of 15 decimals, so if you have larger numbers (or if you have more than 15 decimals, before and after the comma), doubles will never exactly hold the value you intended to.
Single precision floats only have an accuracy of 7 decimals. In most cases this is sufficient.

Just to set this straight.. a single is accurate to 7 places and not to 7 places after the decimal point and so it is not sufficient in most any cases that add monetary values eg accounting software, business etc

Private Sub Command1_Click()
    Dim lVar As Single
    Dim lVar2 As Single
    
    lVar = 23456.78
    lVar2 = 33456.31
    Debug.Print lVar + lVar2 '56913.09
 
    lVar = 123456.78
    lVar2 = 133456.31
    Debug.Print lVar + lVar2 '256913.1
 
    lVar = 1023456.78
    lVar2 = 1033456.31
    Debug.Print lVar + lVar2 '2056913
 
    lVar = 51023456.78
    lVar2 = 51033456.31
    Debug.Print lVar + lVar2 '1.020569E+08
End Sub

Hence the scientific notation that comes in after 7 places are used up.
Regards

[nishantp]

Originally posted by rjlohan
Double is to Single as Long is to Integer.

Double and Single are both floating-point variables. The double can hold numbers twice as big. If you make them sufficiently large, they start displaying in scientific notation, and I think you may lose a small amount of accuracy.

Spreading false information are we?
1.79769313486231E+308 is one hell of a lot more than twice as large as 3.402823E+38.

[rjlohan]

Originally posted by nishantp
Spreading false information are we?
1.79769313486231E+308 is one hell of a lot more than twice as large as 3.402823E+38.

I didn't mean it like that. I was referring to the level of accuracy, and the number of bits for the storage of the number really...