XL2000: How to Use the Imp Operator for Binary Comparison (213706)

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The syntax for the Imp operator is as follows where expression1 and expressions2 are any expressions and result is any numeric variable.

When you use the Imp operator to perform a bit-wise comparison of identically positioned bits in two numeric expressions, the result of the bit-wise comparison is determined using the rules in the following table.

   Bit in Expression1   Bit in Expression2   Bit in Result
   -------------------------------------------------------
           1                     1                 1
           1                     0                 0
           0                     1                 1
           0                     0                 1
				

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Sub Imp_Example()

Dim a As Integer
Dim b As Integer
Dim result As Integer

   a =10
   b = 4

   result = a Imp b

   MsgBox result

End Sub
				

The value -11 is returned because the macro follows the rules in the table and uses twos complement notation. Using twos complement notation, the leftmost bit represents the sign bit. If this bit is 1, the number is negative; if this bit is 0 (zero), the number is positive. To convert a negative number from binary back to decimal, complement all of the bits (1 becomes 0 and 0 becomes 1), convert that number to decimal, change the sign of the decimal number, and then subtract 1.

In the example, where the Imp operator is used with the two numeric values 10 and 4. In binary form (2 bytes), these two numbers appear as follows:

   10:   0000000000001010
    4:   0000000000000100
				

Using the bit-wise comparison rules from the table yields the result value in binary form:

   10:   0000000000001010

    4:   0000000000000100
   --------------------------

   result:   1111111111110101
				

To determine the decimal equivalent of the result, use the twos complement rules of conversion as follows:

                                  Result: 1111111111110101

                     Complement each bit: 0000000000001010

Decimal equivalent of this binary number: 10

                 Opposite of this number: -10
    Subtract 1 (decimal value of result): -11