artefactop · July 24, 2013 09:31 · Jul 24, 2013
diff --git a/get_random b/get_random
@@ -0,0 +1,51 @@
+#!/usr/bin/env escript
+
+main([NS, SL]) ->
+    try
+        N = list_to_integer(NS),
+        List = eval(SL),
+        io:format("Result: ~p~n", [random(List,N)])
+    catch
+        _:_ ->
+            usage()
+    end;
+main(Input) ->
+    io:format("Input: ~p~n", [Input]),
+    usage().
+
+usage() ->
+    io:format("usage: random N [ele1,ele2,ele3,ele4]\n"),
+    halt(1).
+
+random(L, N) ->
+    random(list_to_tuple(L), N, []).
+
+random({},_,Acc) ->
+    Acc;
+random(_,0,Acc) ->
+    Acc;
+random(T, N, Acc) ->
+    {A1,A2,A3} = os:timestamp(),
+    random:seed(A1, A2, A3),
+    Rand = random:uniform(size(T)),
+    E = erlang:element(Rand, T),
+    random(delete_element(Rand, T), N-1, Acc ++ [E]).
+
+delete_element(N,T) -> %% change for erlang:delete_element
+    L = erlang:tuple_to_list(T),
+    Ele = erlang:element(N, T),
+    erlang:list_to_tuple(lists:filter(fun(X) -> X =/= Ele end, L)). %%BUG when exits duplicate elements
+
+eval(S) ->
+    Last = lists:last(S),
+    if 
+        Last =/= 46 ->
+            eval(S ++ ".",[]);
+        true ->
+            eval(S,[])
+    end.
+eval(S,Environ) ->
+    {ok,Scanned,_} = erl_scan:string(S),
+    {ok,Parsed} = erl_parse:parse_exprs(Scanned),
+    {value, R, _} = erl_eval:exprs(Parsed,Environ),
+    R.