is_x functionfunction is_x ( s : std_ulogic ) return boolean;function is_x ( s : std_ulogic_vector ) return boolean;function is_x ( s : std_logic_vector ) return boolean;
For a std_ulogic or std_logic argument, this function returns true if the value is one of the undefined values (
'U',
'X',
'Z',
'W',
'-'). It returns false otherwise.
If the argument is a vector, the function returns true if any of the elements in the would have is_x true.