loop.erl

-module(loop).
-export([for/2, for/4, while/2, repeat/2]).

%%% Let's make Erlang great again!

% Look, today we are going to fix the glaring omission,
% I promise you that.
% We are going to build a loop module for Erlang!
% A loop module for Erlang, yes!

for([], _Fun) -> [];
for([H | T], Fun) ->
    Fun(H), for(T, Fun).

for(Start, Cond, Step, Fun) ->
    I = Start(),
    C = Cond(I),
    if
    C ->
       Fun(I),
       for(fun() -> Step(I) end, Cond, Step, Fun);
    true ->
       ok
    end.

% if you need state here, use actors or whatever, now it's your problem
while(Cond, Fun) ->
    C = Cond(),
    if C    -> Fun(), while(Cond, Fun);
       true -> ok
    end.

% see the comment for `while/2`
repeat(Fun, Cond) ->
    Fun(),
    while(Cond, Fun).