VHDL Syntax :        bit operators

VHDL has the following operators that act on type bit

not
and   or
nand  nor
xor   xnor

The precedence rules are different to the normal precedence of boolean algebra
'not' has the highest precedence
'and', 'or', 'nand', 'nor', 'xor', 'xnor' have equal precedence
SO