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#1
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Overflow when translating from C++ HELP!!
Hello everyone,
I am having issues translating something from C++ to VBA due to overflow. As soon as I get to the end of this function, the routine dies. It calculates a value, and I can get down to the last line in the function (End Function) and everything is fine. As soon as I hit F8 one more time, it chokes. I got the function below from vbAccelerator ... it is supposed to be able to do unsigned left and right shifts in VBA while avoiding overflow. If there is something wrong with the function, what is it? If not, am I passing a bad argument? Can anyone help? The m_lPower2(i) variable is just equal to 2^i for i = 0 to 31. Public Function RShift(ByVal lThis As Long, ByVal lBits As Long) As Long If (lBits <= 0) Then RShift = lThis ElseIf (lBits 63) Then ' .. error ... ElseIf (lBits 31) Then RShift = 0 Else If (lThis And m_lPower2(31 - lBits)) = m_lPower2(31 - lBits) Then RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits) Or m_lPower2(31) Else RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits) End If End If End Function *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#2
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Overflow when translating from C++ HELP!!
What is the m_lPower2 function doing? Perhaps you could provide
the code for that function. -- Cordially, Chip Pearson Microsoft MVP - Excel Pearson Software Consulting, LLC www.cpearson.com "hunting" wrote in message ... Hello everyone, I am having issues translating something from C++ to VBA due to overflow. As soon as I get to the end of this function, the routine dies. It calculates a value, and I can get down to the last line in the function (End Function) and everything is fine. As soon as I hit F8 one more time, it chokes. I got the function below from vbAccelerator ... it is supposed to be able to do unsigned left and right shifts in VBA while avoiding overflow. If there is something wrong with the function, what is it? If not, am I passing a bad argument? Can anyone help? The m_lPower2(i) variable is just equal to 2^i for i = 0 to 31. Public Function RShift(ByVal lThis As Long, ByVal lBits As Long) As Long If (lBits <= 0) Then RShift = lThis ElseIf (lBits 63) Then ' .. error ... ElseIf (lBits 31) Then RShift = 0 Else If (lThis And m_lPower2(31 - lBits)) = m_lPower2(31 - lBits) Then RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits) Or m_lPower2(31) Else RShift = (lThis And (m_lPower2(31 - lBits) - 1)) * m_lPower2(lBits) End If End If End Function *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#3
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Overflow when translating from C++ HELP!!
Chip, Thanks so much for being willing to take a look at this. The m_lPower2() variables are set in a Sub that is called prior to the code I gave earlier. Here it is. Any help you can provide would be thoroughly appreciated. Best regards. Public Sub InitPowers() m_lPower2(0) = &H1& m_lPower2(1) = &H2& m_lPower2(2) = &H4& m_lPower2(3) = &H8& m_lPower2(4) = &H10& m_lPower2(5) = &H20& m_lPower2(6) = &H40& m_lPower2(7) = &H80& m_lPower2(8) = &H100& m_lPower2(9) = &H200& m_lPower2(10) = &H400& m_lPower2(11) = &H800& m_lPower2(12) = &H1000& m_lPower2(13) = &H2000& m_lPower2(14) = &H4000& m_lPower2(15) = &H8000& m_lPower2(16) = &H10000 m_lPower2(17) = &H20000 m_lPower2(18) = &H40000 m_lPower2(19) = &H80000 m_lPower2(20) = &H100000 m_lPower2(21) = &H200000 m_lPower2(22) = &H400000 m_lPower2(23) = &H800000 m_lPower2(24) = &H1000000 m_lPower2(25) = &H2000000 m_lPower2(26) = &H4000000 m_lPower2(27) = &H8000000 m_lPower2(28) = &H10000000 m_lPower2(29) = &H20000000 m_lPower2(30) = &H40000000 m_lPower2(31) = &H80000000 End Sub *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#4
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Overflow when translating from C++ HELP!!
The code works fine for me (Excel2003). I can't get an overflow
error unless the m_lPower2 array is declared as Integer. -- Cordially, Chip Pearson Microsoft MVP - Excel Pearson Software Consulting, LLC www.cpearson.com "hunting" wrote in message ... Chip, Thanks so much for being willing to take a look at this. The m_lPower2() variables are set in a Sub that is called prior to the code I gave earlier. Here it is. Any help you can provide would be thoroughly appreciated. Best regards. Public Sub InitPowers() m_lPower2(0) = &H1& m_lPower2(1) = &H2& m_lPower2(2) = &H4& m_lPower2(3) = &H8& m_lPower2(4) = &H10& m_lPower2(5) = &H20& m_lPower2(6) = &H40& m_lPower2(7) = &H80& m_lPower2(8) = &H100& m_lPower2(9) = &H200& m_lPower2(10) = &H400& m_lPower2(11) = &H800& m_lPower2(12) = &H1000& m_lPower2(13) = &H2000& m_lPower2(14) = &H4000& m_lPower2(15) = &H8000& m_lPower2(16) = &H10000 m_lPower2(17) = &H20000 m_lPower2(18) = &H40000 m_lPower2(19) = &H80000 m_lPower2(20) = &H100000 m_lPower2(21) = &H200000 m_lPower2(22) = &H400000 m_lPower2(23) = &H800000 m_lPower2(24) = &H1000000 m_lPower2(25) = &H2000000 m_lPower2(26) = &H4000000 m_lPower2(27) = &H8000000 m_lPower2(28) = &H10000000 m_lPower2(29) = &H20000000 m_lPower2(30) = &H40000000 m_lPower2(31) = &H80000000 End Sub *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#5
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Overflow when translating from C++ HELP!!
Chip,
Again, thank you for taking time with this. Would you field one more question for me? Perhaps the error is generated immediately after the function calculates, and then returns to the main subroutine? It looks like this: mt(0) = (s And &HFFFFFFFF) For mti = 1 To N - 1 mt(mti) = 1812433253 * (mt(mti - 1) Xor (RShift(mt(mti - 1), 30)) + mti) Next mti mt(mti) = &HFFFFFFFF Best regards, Nick *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#6
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Overflow when translating from C++ HELP!!
The XOR operator can only handle signed Longs, and your
expression 'mt(mti - 1)' is greater than the maximum value of a Long (I get 1.33E+18). If you are using XOR, you are limited to Longs. -- Cordially, Chip Pearson Microsoft MVP - Excel Pearson Software Consulting, LLC www.cpearson.com "hunting" wrote in message ... Chip, Again, thank you for taking time with this. Would you field one more question for me? Perhaps the error is generated immediately after the function calculates, and then returns to the main subroutine? It looks like this: mt(0) = (s And &HFFFFFFFF) For mti = 1 To N - 1 mt(mti) = 1812433253 * (mt(mti - 1) Xor (RShift(mt(mti - 1), 30)) + mti) Next mti mt(mti) = &HFFFFFFFF Best regards, Nick *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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#7
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Overflow when translating from C++ HELP!!
Chip,
Thanks again. So this is the point at which overflow occurs. Would you be able to provide me with any references to a workaround? Or any tips to accomplish this operation? Best, Nick *** Sent via Developersdex http://www.developersdex.com *** Don't just participate in USENET...get rewarded for it! |
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