tailrecursion.erl

untitled

-module(tailrecursion).
-export([fac/1,loop/1,sum/1,maximum/1,fib/1,perfect/1]).

fac(N) -> fac(N,1).
fac(0,P) ->
  P;
fac(N,P) when N>0 ->
  fac(N-1,P*N).

loop(N) when N>0 ->
  io:format("~p~n",[N]),
  loop(N-1);
loop(_) ->
  io:format("bye~n").

sum(N) -> sum(N,0).
sum(0,P) -> P;
sum(N,P) when N>0 ->
  sum(N-1,N+P).

maximum(N) -> maximum(N,0).
maximum(0,P) -> P;
maximum(N,P) when N>0 ->
  case N>P of
      true -> maximum(N-1,N);
      false -> maximum(N-1,P)
  end.

fib(0) -> 0;
fib(1) -> 1;
fib(N) -> fib(N,1,0).
fib(1,P1,P2) ->
  P1+P2;
fib(N,P1,P2) when N>0 ->
  fib(N-1,P1+P2,P1).

perfect(N) -> perfect(N,N div 2,0).
perfect(N,0,N) -> true;
perfect(_,0,_) -> false;
perfect(N,P,A) when N rem P == 0 -> perfect(N,P-1,A+P);
perfect(N,P,A) -> perfect(N,P-1,A).