erlang-higher-order.erl

% map/2
Map = fun lists:map/2.
  % increment using anon fn
  Map(fun(X) -> X + 1 end, [1,2,3,4]).
  % find powers of two
  PowerOfTwo = fun(X) -> math:pow(2, X) end.
  Map(PowerOfTwo, [1,2,3,4]).

% filter/2
Filter = fun lists:filter/2.
  % keep evens
  Filter(fun(X) -> X rem 2 == 0 end, lists:seq(1,10)).
  % keep CS majors
  Filter(fun({Major, _}) -> Major == cs end, [{cs, alice}, {ece, bob}, {cs, charlie}]).

% foldl/3
Foldl = fun lists:foldl/3.
  % summation
  Foldl(fun(X, Sum) -> Sum + X end, 0, [1,2,3,4,5]).
  % reversing a list
  Foldl(fun(X, R) -> [X|R] end, [], [1,2,3,4,5]).

% More higher-order functions
IsSmall = fun(X) -> X < 3 end.
lists:all(IsSmall, [0,1,2]).          % => true
lists:all(IsSmall, [0,1,2,3]).        % => false
lists:any(IsSmall, [0,1,2,3]).        % => true
lists:any(IsSmall, [3,4]).            % => false
lists:takewhile(IsSmall, [1,2,3,4]).  % => [1,2]
lists:dropwhile(IsSmall, [1,2,3,4]).  % => [3,4]