% hello world program
-module(helloworld).
-export([start/0]).

start() ->
    io:fwrite("Hello, world!\n"),
    Ciag="a * b + c / d",
    Infix=string:tokens(Ciag, " "),
    io:fwrite("Notacja infiksowa: ~p~n", [Infix]),
    {X,Y}=infixToPrefix(Infix,7,[],[]),
    io:fwrite("Notacja prefiksowa: ~p~n", [Y]).


infixToPrefix(Str,N,L1,L2) when N==0 ->
    {L1,lists:append(lists:reverse(L1),L2)};

infixToPrefix(Str,N,L1,L2) when N>0 ->

Element=lists:nth(N,Str),
{X,Y} = case Element of
    "+" ->
        if
            length(L1)==0 -> {lists:append([Element,L1]),L2};
            length(L1)>0 ->
                El=lists:nth(1,L1),
                if
                    [El] == "+" -> {lists:append([Element,L1]),L2};
                    [El] == "-" -> {lists:append([Element,L1]),L2};
                    [El] == "*" ->
                    Temp=lists:delete(El,L1), % tutaj musze usunąć El
                    {lists:append(Element,Temp), lists:append([[El],L2])};
                    [El] == "/" ->
                    Temp=lists:droplast(L1),
                    {lists:append(Element,Temp), lists:append([[El],L2])};
                true -> io:fwrite("else")
                end;
        true -> io:fwrite("else")
        end;
    "-" ->
         if
            length(L1)==0 -> {lists:append([Element,L1]),L2};
            length(L1)>0 ->
                El=[lists:nth(1,L1)],
                if
                    [El] == "+" -> {lists:append([Element,L1]),L2};
                    [El] == "-" -> {lists:append([Element,L1]),L2};
                    [El] == "*" ->
                    Temp=lists:delete(El,L1),
                    {lists:append(Element,Temp), lists:append([[El],L2])};
                    [El] == "/" ->
                    Temp=lists:droplast(L1),
                    {lists:append(Element,Temp), lists:append([[El],L2])};
                true -> io:fwrite("else")
                end;
        true -> io:fwrite("else")
        end;
    "*" ->
         if
            length(L1)==0 -> {lists:append([Element,L1]),L2};
            length(L1)>0 ->
                El=[lists:nth(1,L1)],
                if
                    El == "+" -> {lists:append([Element,L1]),L2};
                    El == "-" -> {lists:append([Element,L1]),L2};
                    El == "*" -> {lists:append([Element,L1]),L2};
                    El == "/" -> {lists:append([Element,L1]),L2};
                true -> io:fwrite("else")
                end;
        true -> io:fwrite("else")
        end;
    "/" ->
         if
            length(L1)==0 -> {lists:append([Element,L1]),L2};
            length(L1)>0 ->
                El=[lists:nth(1,L1)],
                if
                    El == "+" -> {lists:append([Element,L1]),L2};
                    El == "-" -> {lists:append([Element,L1]),L2};
                    El == "*" -> {lists:append([Element,L1]),L2};
                    El == "/" -> {lists:append([Element,L1]),L2};
                true -> io:fwrite("else")
                end;
        true -> io:fwrite("else")
        end;

    _ -> {L1,lists:append([Element,L2])}
    end,

    io:fwrite("Znaki: ~p~n", [X]),
    io:fwrite("Litery: ~p~n", [Y]),
    io:fwrite("*********************\n"),
    infixToPrefix(Str,N-1,X,Y).