In the previous version of VHDL, operators such as and , nand , or , took two different values and then returned a bit or boolean value. For VHDL-2008, unary support has been added for these operators. They return the logical function of the input. For example, the code:
out1 <= and("0101");
would AND the 4 bits together and return 0 . The logical functions have unary support are: and , nand , or , nor , xor , and xnor .