f3.erl

-module(f3).
-export([double/1,evens/1,sort/1,minimum/1,median/1,elem/2,elem/3,modesElem/2,modesElem/3,maxT/1,maxT2/2,modes/1,fst/1,occur/1]).

double([X]) -> [X * 2];
double([X|XS]) -> [(X * 2) | double(XS)].

evens([X]) -> [X];
evens([X|XS]) -> case (X rem 2 == 0)  of
	true -> [X | evens(XS)];
	false -> evens(XS)
end.


sort([X]) -> [X];
sort([X|XS]) -> case (X == minimum([X|XS]))  of
	true -> [X | sort(XS)];
	false -> sort(XS ++ [X])
end.

minimum([X]) -> X;
minimum([X|XS]) -> min(X,minimum(XS)).



elem(L,N) -> elem(L,N,0).

elem([X|XS],N,C) -> case (N == C)  of
	true -> X;
	false -> elem(XS,N,C+1)
end.

median([X]) -> [X];
median(L) ->  
  M = length(L) div 2,
  S = sort(L),
  case (length(L) rem 2 == 0)  of
	true -> 
	  (elem(S,M) + elem(S,M-1)) / 2;
	false -> 
	   elem(S,M)
end.

fst({A,_}) -> A.

maxT([X]) -> X;
maxT([X|XS]) -> maxT2(X,maxT(XS)).

maxT2({A,B},{C,D}) -> case (B > D)  of
	true -> {A,B};
	false -> {C,D}
end.


modes(L) -> fst(maxT(occur(L))).

occur([X]) -> [{X,1}];
occur([X|XS]) -> [ {X, modesElem([X|XS],X)} | occur(XS)].

modesElem(L,E) -> modesElem(L,E,0).

modesElem([X],E,C) -> case (X == E)  of
	true -> C+1;
	false -> C
end;

modesElem([X|XS],E,C) -> case (X == E)  of
	true -> modesElem(XS,E,C+1);
	false -> modesElem(XS,E,C)
end.