RosettaCodeData/Task/Euler-method/Erlang/euler-method.erl

-module(euler).
-export([main/0, euler/5]).

cooling(_Time, Temperature) ->
    (-0.07)*(Temperature-20).

euler(_, Y, T, _, End) when End == T ->
    io:fwrite("\n"),
    Y;

euler(Func, Y, T, Step, End) ->
    if
        T rem 10 == 0 ->
            io:fwrite("~.3f  ",[float(Y)]);
        true ->
            ok
    end,
    euler(Func, Y + Step * Func(T, Y), T + Step, Step, End).

analytic(T, End) when T == End ->
    io:fwrite("\n"),
    T;

analytic(T, End) ->
    Y = (20 + 80 * math:exp(-0.07 * T)),
    io:fwrite("~.3f  ", [Y]),
    analytic(T+10, End).

main() ->
    io:fwrite("Analytic:\n"),
    analytic(0, 100),
    io:fwrite("Step 2:\n"),
    euler(fun cooling/2, 100, 0, 2, 100),
    io:fwrite("Step 5:\n"),
    euler(fun cooling/2, 100, 0, 5, 100),
    io:fwrite("Step 10:\n"),
    euler(fun cooling/2, 100, 0, 10, 100),
    ok.