meaning of higher order
1.   higher-order function HOF A function that can take one or more functions as argument and/or return a function as its value.   E. g.  map in map f l which returns the list of results of applying function f to each of the elements of list l.   See also curried function.  higher-order macro A means of expressing certain higher-order functions in a first order language.   Proposed by Phil Wadler.   Higher-order macros cannot be recursive at the top level but they may contain recursive definitions.   E. g.  map f l = m l   where   m []   = []   m x:xs = f x : m xs Expanding a call to this macro is equivalent to specialising a call to map in its first argument.  See partial evaluation.  High-level Data Link Control 
						 
