COMPLEMENT()
 Forms the complement value of a data type
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 Syntax

     COMPLEMENT(<expValue>) --> xComplement

 Argument

     <expValue>[@]  Designates any valid expression of any data type to
     form a complement value.  Complement() only allows a character string to
     be passed by reference.

 Returns

     COMPLEMENT() returns the complement value that corresponds to the same
     data type for <expValue>.

 Description

     COMPLEMENT() returns the respective opposite value of the <expValue>
     parameter.  In contrast to CHARNOT(), which only permits character
     strings, this function permits all data types.  The result is the same
     data type as the parameter.  For example, a date returns a date as a
     result.  It corresponds to the difference between the indicated date and
     12/31/2999.

 Note

     .  COMPLEMENT(COMPLEMENT(<expValue>)) always returns <expValue>
        as output.

 Examples

     .  The complement of a logical value corresponds to the use of
        .NOT.:

        ? COMPLEMENT(.T.)                  // .F.
        ? COMPLEMENT(.F.)                  // .T.

     .  Numeric values change sign:

        ? COMPLEMENT(99)                   // -99.00
        ? COMPLEMENT(0)                    // 0
        ? COMPLEMENT(-99)                  // 99.00
        ? COMPLEMENT(-9.9)                 // 9.90
        ? COMPLEMENT(9.9)                  // -9.9

     .  With strings, the function works like CHARNOT:

        ? COMPLEMENT("123ABCabc")          // "       <157><156>"

     .  The difference between 1/1/1900 and 01/01/3000:

        SET CENTURY ON
        ? COMPLEMENT(CTOD("01/01/00"))     // 12/31/1099

     .  An empty or invalid date gives the same result -- 01/01/3000:

        SET CENTURY ON
        ? COMPLEMENT(CTOD("  /  /  "))     // 01/01/3000
        ? COMPLEMENT(CTOD("77/77/77"))     // 01/01/3000