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Thread: Mod function

081506, 18:54 #1Registered User
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 Aug 2006
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Unanswered: Mod function
I have been looking at the mod function in access and it doesn't like it when processing very large numbers.
Does anyone know how I can calculate the mod of a very large number easily in access?
Thanks for your help

081506, 21:28 #2Moderator
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 Jun 2005
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Provided Answers: 19What are you calling large numbers?
Hope this helps!
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007

081606, 12:17 #3Registered User
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 Apr 2003
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 Alabama, USA
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MOD only handles LONG numbers.
Try this
Code:Instead of num MOD div Use num  div * INT(num/div)

081606, 12:33 #4Moderator
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Provided Answers: 19Actually MOD works with any numeric expression.
Hope this helps!
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007

081606, 12:54 #5Registered User
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 Apr 2003
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 Alabama, USA
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Originally Posted by Missinglinq
Also MOD treats the number as a whole number (no decimals).
Code:2147483646.5 MOD 2 = 0 2147483646.5  2 * INT(2147483646.5/2) = 0.5
Last edited by Cosmos75; 081606 at 13:06.

081606, 14:40 #6Cavalier King Charles
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 Dec 2002
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interesting!
here's an outline attempt to explode the longlimit.
the code below should achieve X = Y Mod Z for
Y = 922,337,203,685,477
Z = 30,000,000
most likely you could modify the outline to use Double datatypes and extend the range to
Y = something x 10^308
Z = something x 10^154
the outline code is full of debug lines and is not bulletproofed.
very small Y, Z (e.g. 0, 1) have not been investigated or guarded against
...but you did say 'very large numbers'!
check the results from the algo before using it for real. i don't have an independent Mod tool to compare my results with but the algo seems reasonable.
izy
Code:Private Sub GO_Click() Dim X As Currency ' X = Y mod Z Dim Y As Currency Dim Z As Currency Dim i As Integer 'max power Dim j As Currency 'holder for current Z^k Dim k As Integer 'actual power Const lMax As Long = 2147483647 'longinteger limit Const cMax As Currency = 922337203685477# 'Currency limit Const zMax As Long = 30000000 'max allowed Z in Y Mod Z (set to 922337203685477^0.5) Dim a As Long 'a counter for debug  not used in calcs 'get test data from a form Y = Me.numY Z = Me.numZ Debug.Print "" Debug.Print "Calculate X = Y mod Z" Debug.Print "Y:"; Y, "Z:"; Z 'boundary If Z > zMax Then MsgBox "Z is too large for this algorithm", vbCritical, "Overflow risk!" Me.numX = "Illegal input" Exit Sub End If 'plan is to reduce Y by successive subtractions of 'Z^i, Z^(i1), Z^(i2)... etc 'until residualY is <= lMax 'Z^i must not overflow datatype i = 1 Do While Z ^ i < cMax / Z i = i + 1 Loop Debug.Print "BEGIN powers subtraction" For k = i To 1 Step 1 j = Z ^ k If ((j < Z) Or (Y < lMax)) Then Exit For 'do not kill the remainder or loop too much a = 0 Do While Y > j Y = Y  j a = a + 1 Loop Debug.Print "Loops:"; a, "k:"; k, "j:"; j, "Y:"; Y Next Debug.Print "END powers subtraction loop with Y:"; Y 'Y is now significantly smaller 'should be small enough (j<Z and lMax) '<<< LATER: and not zMax as i said the first time round 'but just to make sure... Do While Y > lMax Y = Y  Z Debug.Print "brute force subtraction:", Y Loop 'calculate mod X = Y Mod Z Debug.Print "Custom algo result X:", X 'post the result Me.numX = X End Sub
Code: Calculate X = Y mod Z Y: 922337203685477 Z: 30000000 BEGIN powers subtraction Loops: 1 k: 2 j: 900000000000000 Y: 22337203685477 Loops: 744573 k: 1 j: 30000000 Y: 13685477 END powers subtraction loop with Y: 13685477 Custom algo result X: 13685477  Calculate X = Y mod Z Y: 922337203685477 Z: 30000 BEGIN powers subtraction Loops: 34 k: 3 j: 27000000000000 Y: 4337203685477 Loops: 4819 k: 2 j: 900000000 Y: 103685477 END powers subtraction loop with Y: 103685477 Custom algo result X: 5477  Calculate X = Y mod Z Y: 922337203685477 Z: 30 BEGIN powers subtraction Loops: 1 k: 10 j: 590490000000000 Y: 331847203685477 Loops: 16 k: 9 j: 19683000000000 Y: 16919203685477 Loops: 25 k: 8 j: 656100000000 Y: 516703685477 Loops: 23 k: 7 j: 21870000000 Y: 13693685477 Loops: 18 k: 6 j: 729000000 Y: 571685477 END powers subtraction loop with Y: 571685477 Custom algo result X: 17  Calculate X = Y mod Z Y: 922337203685 Z: 30000000 BEGIN powers subtraction Loops: 0 k: 2 j: 900000000000000 Y: 922337203685 Loops: 30744 k: 1 j: 30000000 Y: 17203685 END powers subtraction loop with Y: 17203685 Custom algo result X: 17203685  Calculate X = Y mod Z Y: 20000000000001 Z: 10 BEGIN powers subtraction Loops: 0 k: 14 j: 100000000000000 Y: 20000000000001 Loops: 2 k: 13 j: 10000000000000 Y: 1 END powers subtraction loop with Y: 1 Custom algo result X: 1
Last edited by izyrider; 081606 at 14:45.
currently using SS 2008R2