Binary Addition of Strings UDF issue

[Juggler_IN]

I am facing an issue with a C++ code conversion to VBA. If you provide two binary strings the function outputs the addition of two strings in binary format.

For example, if a = 11 == "00001011" and b = 36 == 00100100, then a+b = 47 == 00101111. The function also outputs 00101111.

If we provide string input, say within 1,25 using RANDBETWEEN using DEC2BIN then this function in most instances gives the desired output except for few exceptions such as, if a = 11 == 00001011 and b = 35 == 00100011, then a+b = 46 and the output SHOULD be 00101110 but the function is EVALUATING to 00110010 == 50.

I am unable to decode the issue. Any thoughts?

My UDF is:

Private Function solve( _
        ByVal a As String, _
        ByVal b As String) As String

    Dim na%, nb%
    Dim carry%
    Dim i%, j%, k%
    Dim addA%, addB%, sum%
    Dim u, v, ret$

    ret = ""
    na = VBA.Len(a)
    nb = VBA.Len(b)
    i = (na - 1)
    j = (nb - 1)
    carry = 0

    ReDim u(0 To i)
    ReDim v(0 To j)

    For k = 0 To na - 1
        u(k) = VBA.Mid(a, k + 1, 1)
        Debug.Print u(k);
    Next
    Debug.Print

    For k = 0 To nb - 1
        v(k) = VBA.Mid(b, k + 1, 1)
        Debug.Print v(k);
    Next
    Debug.Print

    Do While ((i >= 0) Or (j >= 0))

        If (i >= 0) Then
            addA = (u(i) - VBA.ChrW(48))
        Else
            addA = 0
        End If

        If (j >= 0) Then
            addB = (v(j) - VBA.ChrW(48))
        Else
            addB = 0
        End If

        sum = addA + addB + carry
        carry = sum / 2&
        sum = sum Mod 2&
        ret = ret & "" & sum
        i = (i - 1)
        j = (j - 1)

    Loop

    If carry <> 0 Then
        ret = ret & "" & carry
    End If

    solve = VBA.StrReverse(ret)
    Exit Function

End Function

C++ source code is -- (The link below provides a online execution of this code with different values.)

class Solution {
   public:
   string solve(string a, string b){
      string ret = "";
      int na = a.size();
      int nb = b.size();
      int i = na - 1;
      int j = nb - 1;
      int carry = 0;
      while(i >= 0 || j >= 0){
         int addA = i >= 0 ? a[i] - '0' : 0;
         int addB = j >= 0 ? b[j] - '0' : 0;
         int sum = addA + addB + carry;
         carry = sum / 2;
         sum %= 2;
         ret += to_string(sum);
         i--;
         j--;
      }
      if(carry)
         ret += to_string(carry); reverse(ret.begin(), ret.end());
         return ret;
   }
};
main(){
   string a = "10110", b = "10010"; Solution ob;
   cout << ob.solve(a, b);
}

The C++ source code is atBinary Addition

 

[Rick Rothstein]

What about just using Excel's built-in functions directly...

Function BinaryAdd(BinStr1 As String, BinStr2 As String) As String
  With Application
    BinaryAdd = Format(.Dec2Bin(.Bin2Dec(BinStr1) + .Bin2Dec(BinStr2)), "00000000")
  End With
End Function

 

[Juggler_IN]

@Rick Rothstein ; Thanks, I do have this direct version but am interested in the execution as per the c++ code. I am unable to debug the issue in VBA version. Any thoughts?

 

[Rick Rothstein]

How about this then...

Function BinaryAdd(BinStr1 As String, BinStr2 As String) As String
  Dim X As Long, Temp As Long, Carry As Long
  BinStr1 = Format(BinStr1, "00000000")
  BinStr2 = Format(BinStr2, "00000000")
  BinaryAdd = "00000000"
  For X = 8 To 1 Step -1
    Temp = CLng(Mid(BinStr1, X, 1)) + CLng(Mid(BinStr2, X, 1)) + Carry
    If Temp > 1 Then
      Mid(BinaryAdd, X) = Temp Mod 2
      Carry = 1
    Else
      Mid(BinaryAdd, X) = Temp
      Carry = 0
    End If
  Next
End Function

 

[Juggler_IN]

@Rick Rothstein ; thanks ... this works.

 

[kvsrinivasamurthy]

Try this

Function AddBinary(BStr1 As String, BStr2 As String) As String
Dim K As String
Dim temp As Long
Dim T As Integer, TA As Integer, Mul As Integer

For T = 1 To 2
If T = 1 Then K = BStr1 Else K = BStr2
Mul = 1
    For TA = 1 To Len(K)
    temp = temp + Mul * Mid(K, Len(K) - TA + 1, 1)
    Mul = Mul * 2
    Next TA
Next T

K = ""
Do While temp > 1
K = temp Mod 2 & K
temp = Int(temp / 2)
Loop

AddBinary = Format(temp & K, "00000000")
End Function

 

[Juggler_IN]

@Rick Rothstein ; can we modify the udf for subtraction?

 

[Juggler_IN]

@kvsrinivasamurthy ; the code works for 8 bits but fails for 32. Rick's UDF is more universal. Thanks.