Division of Integer Strings

[Juggler_IN]

While working on Big Integer arithmetic I cam across a post at StackExchange. Is there a way to accept integers of length greater than 15?

Function SuperMod2(ByVal a$, b$)
    Do While Len(a) > 15
        a = Mid$(a, 1, 15) - Int(Mid$(a, 1, 15) / b) * b & Mid$(a, 16)
    Loop
    SuperMod2 = a - Int(a / b) * b
End Function

This version allows for:
SuperMod2("654654321902010548705495321500805040401121210900506078798456849816241968462130000051204789540453745898347543753489751261610093245892737467263468234623689898054456361110010151021101827", 999999999999999)
... to correctly display: 194745570864677.

 

[maabadi]

Change Dim integers to Long

 

[Joe4]

While working on Big Integer arithmetic I cam across a post at StackExchange. Is there a way to accept integers of length greater than 15?

Change Dim integers to Long

I don't think that will work. Excel can only remember up to 15 significant digits, and I believe VBA is the same.
Tests seem to confirm this. Try entering any number more than 15 digits, and you will see that.

The way to get it to remember more is to convert it to text, but then you would not be able to do arithmetic operations on it.

 

[Rick Rothstein]

This won't handle numbers anywhere near as large as your question posed, but it will hand numbers (inputted as text) larger than 15 digits...

'  The arguments to the BigMod function can be up to 29 digits as long as
'  either number is less than 79,228,162,514,264,337,593,543,950,335
'  (a limitation of the Decimal data type used in the calculations).
'  And, of course, if you are going to feed the BigMod function super
'  large numbers, they must be passed in as quoted text strings.
Function BigMod(Number As Variant, Modulus As Variant) As Variant
  Number = CDec(Number)
  Modulus = CDec(Modulus)
  BigMod = Number - Modulus * Int(Number / Modulus)
End Function

 

[Joe4]

Rick,

What do they need to use for the "Modulus" argument/parameter when using that function?
Might be helpful to show an example, so they can see how to use it.

 

[Rick Rothstein]

What do they need to use for the "Modulus" argument/parameter when using that function?

Any number up to the 29 digits... same as the number whose modulus is being calculated. For example, let's say we wanted to find 9876543210987654321098765432 mod 12345678901234567890 for some reason. You could use it like this...

MsgBox BigMod("9876543210987654321098765432", "12345678901234567890")

or put those numbers in variables and use the variables in the function instead. Now, because Excel likes to convert number automatically, you would need to modify the function slightly to make sure large outputted numbers remain intact...

Function BigMod(Number As Variant, Modulus As Variant) As Variant
  Number = CDec(Number)
  Modulus = CDec(Modulus)
  BigMod = CStr(Number - Modulus * Int(Number / Modulus))
End Function

then you would use something like this on the worksheet...

A1: 9876543210987654321098765432 (Text format)
B1: 12345678901234567890
C1: =BigMod(A1,B1)