Data Type Differences

[kimble]

I'm having a problem with storing large numbers in an array. When I try to assign a 20 digit number from a text box to a variable I get an overflow error. What data type should i assign my variables to allow for these large integers? I've tried Integer and Long.

Here is a simple example:
Placing 123456789123456789 in the textbox

Dim I As Long
I = Text1.Text
MsgBox I

I get 'Run time error' Overflow 6

Any Ideas?

 

[strongm]

Try Double

 

[SmokingCrater]

kimble,

Yep, use Double.

From VB help:

"Long (long integer) variables are stored as signed 32-bit (4-byte) numbers ranging in value from -2,147,483,648 to 2,147,483,647. Thetype-declaration character for Long is the ampersand (&)."

Your number is too long. Whereas Double datatype:

"Double (double-precision floating-point) variables are stored as IEEE 64-bit (8-byte) floating-point numbers ranging in value from -1.79769313486232E308 to -4.94065645841247E-324 for negative values and from 4.94065645841247E-324 to 1.79769313486232E308 for positive values. Thetype-declaration character for Double is the number sign (#)."

Much larger range. Hope that helps.

-crater

 

[kimble]

Is there anyway to store a number longer than 308 digits?

 

[strongm]

I can't actually think - at the moment - of an application that VB is suitable for that would require such an ability. Could you enlighten me?

 

[SmokingCrater]

Kimble,

Yeah, what are you trying to do that will require more than 308 digits? That's one heck of a huge number.

-crater

 

[kimble]

I wrote a prime number algorithm that can find primes between two numbers fast. I used VB cause it was easy. I do know Fortran so maybe I'll try to switch it over and see how long a digit number i can create. Right now the largest known prime numbers have ~ 2 million digits in them.

 

[SmokingCrater]

kimble,

I'm sorry to say, but VB isn't your best option for that I don't think. You won't find a single data type that will take a number with 2 million digits. Not only that, but I don't think you will find any language that has a data type that big.

What you will need to do is to create an array of 2 million items where each item is a digit. Then you can manually manipulate (remember elementary school math where you had to do each digit at a time?) the numbers.

For your problem I might suggest something a little more mathematically oriented. Something of the C/C++ variety.

Hope that helps a bit.

-crater

 

[kimble]

Can you even create an array of 2 million items in any language?

 

[SmokingCrater]

Sure. It just might be slow. And you gotta have enough RAM/Swap Space.

Linked list works well for that too. You don't have a size limit (other than physical limitations like RAM) because there is no counter involved. Arrays might have counters for which 2 million items will overflow.

-crater

 

[rvBasic]

You can always store huge numbers as a string variable. Sadly, VB's standard mathematical operators do not support them. There aren't any built-in function neither.

Fortunately there are some clever and courageous programmers who did the work: it's up to you to grab it at:

http://www.freevbcode.com/ShowCode.Asp?ID=1622

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