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@ptrelford
Created November 7, 2012 07:56
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Erlang sequential programming exercises
-module(crossring).
-compile(export_all).
start(N) ->
Pid = spawn(crossring,first,[N]),
register(cring, Pid),
ok.
send(M, Msg) -> cring ! {1, M, Msg }, ok.
first(N) ->
Next1=spawn(crossring,next,[(N div 2)+1,N,self()]),
First=spawn(crossring,loop,[1,Next1]),
Next2=spawn(crossring,next,[2,N div 2,First]),
loop(1,Next2).
next(N,N,First) ->
loop(N,First);
next(X,N,First) ->
Next=spawn(crossring,next,[X+1,N,First]),
loop(X,Next).
loop(N,Next) ->
receive
{ M, M, _ } ->
io:format("Done",[]),
loop(N,Next);
{ X, M, Msg } ->
io:format("~w ~s~n",[N,Msg]),
Next ! { X + 1, M, Msg },
loop(N,Next)
end.
-module(my_db).
-compile(export_all).
start() ->
Db = [],
register(my_db, spawn(my_db,loop,[Db])),
ok.
call(Message) ->
my_db ! {request, self(), Message},
receive
{ reply, Response } -> Response
end.
stop() -> my_db ! stop.
write(Key,Element) -> call({write, Key, Element}).
delete(Key) -> call({delete, Key}).
read(Key) -> call({read, Key}).
match(Element) -> call({match, Element}).
reply(Client, Msg) -> Client ! { reply, Msg }.
loop(Db) ->
receive
{ request, Client, {write, Key, Element} } ->
reply(Client,ok),
loop([{Key,Element}|Db]);
{ request, Client, {delete, Key, Element} } ->
reply(Client,ok),
loop(lists:keydelete(Key,1,Db));
{ request, Client, {read, Key} } ->
case lists:keyfind(Key,1,Db) of
{_,Value} -> reply(Client, Value);
false -> { error, instance }
end,
loop(Db);
{ request, Client, {match, Element} } ->
Keys = [Key||{Key,Value}<-Db, Value=:=Element],
reply(Client, Keys),
loop(Db);
stop -> ok
end.
-module(ring).
-export([start/1,send/2,first/1,next/3,loop/1]).
start(N) ->
Pid = spawn(ring,first,[N]),
register(pring, Pid),
ok.
send(M, Msg) -> pring ! {1, M, Msg }, ok.
first(N) ->
Next=spawn(ring,next,[2,N,self()]),
loop(Next).
next(N,N,First) ->
loop(First);
next(X,N,First) ->
Next=spawn(ring,next,[X+1,N,First]),
loop(Next).
loop(Next) ->
receive
{ M, M, _ } ->
io:format("Done",[]);
loop(Next).
{ X, M, Msg } ->
io:format("~s~n",[Msg]),
Next ! { X + 1, M, Msg },
loop(Next)
end.
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