资料来源 : Free On-Line Dictionary of Computing

fixed point
     
         The fixed point of a function, f is any value, x
        for which f x = x.  A function may have any number of fixed
        points from none (e.g. f x = x+1) to infinitely many (e.g. f x
        = x).  The {fixed point combinator}, written as either "fix"
        or "Y" will return the fixed point of a function.
     
        See also {least fixed point}.
     
        (1995-04-13)