====== Erlang - Lista 2. ======

===== Zadanie 1. (dude) =====
<file erlang l2-zad1.erl>
#!/usr/bin/env escript

main(Y) ->
        X = toint(Y),
        case length(X) of
                0 ->    io:format("usage: ./seq n [n [n]]~n");
                1 ->    [A] = X,
                        seq(A);
                2 ->    [A, B] = X,
                        seq(A, B);
                3 ->    [A, B, C] = X,
                        seq(A, B, C)
        end.

toint([]) ->    [];
toint([H|T]) -> [list_to_integer(H) | toint(T)].
                                
seq(End) ->             seq(1, End, 1).
seq(Start, End) ->      seq(Start, End, 1).
seq(Cur, End, Step) ->  if      
                                Cur > End ->    done;
                                Cur =< End ->   io:format("~B~n", [Cur]),
                                                seq(Cur+Step, End, Step)
                        end.
</file>
===== Zadanie 2. (dude) =====
<file erlang l2-zad2.erl>
-module(zad2).                  
-export([isum/1, imax/1]).      
                                
isum([]) -> 0;                  
isum([H|T]) when is_integer(H) -> H + isum(T);
isum([H|_]) -> io:format("~p is not an integer~n", [H]).
                                
imax([]) -> 0;                  
imax([H|T]) when is_integer(H) -> Y = imax(T),
        if                      
                H > Y -> H;     
                H =< Y -> Y     
        end;                    
imax([H|_]) -> io:format("~p is not an integer~n", [H]).
</file>
===== Zadanie 3. =====
==== Wersja 1 (Ponton) ====
<file erlang l2-zad3p.erl>
-module(just).
-export([ljust/2, rjust/2, centre/2]).
  
ljust(String, Width) -> just(String, Width, left).
rjust(String, Width) -> just(String, Width, right).
centre(String, Width) -> just(String, Width, centre).
  
just(String, Width, Just) ->
    if
        length(String) > Width -> String;
        true -> shift(String, Width - length(String), Just)
    end.
  
shift(String, 0, _) -> String;
shift(String, 1, centre) -> " " ++ String;
shift(String, N, Just) when N > 0 ->
    case Just of
        left -> shift(" " ++ String, N - 1, Just);
        right -> shift(String ++ " ", N - 1, Just);
        centre -> shift(" " ++ String ++ " ", N - 2, Just)
    end.
</file>
==== Wersja 2 (dude) ====
<file erlang l2-zad3d.erl>
-module(zad3).                  
-export([ljust/2, rjust/2, centre/2]).
                                
gensp(W) when W == 0 -> "";     
gensp(W) -> " " ++ gensp(W-1).  
                                
ljust(S, W) when length(S) >= W -> S;
ljust(S, W) -> S ++ gensp(W - length(S)).
                                
rjust(S, W) when length(S) >= W -> S;
rjust(S, W) -> gensp(W - length(S)) ++ S.

centre(S, W) when length(S) >= W -> S;
centre(S, W) -> rjust(ljust(S, length(S) + (W - length(S))/2), W).
</file>

===== Zadanie 4. (Ponton) =====
<file erlang l2-zad4.erl>
#!/usr/bin/env escript
  
-import(lists).  % tylko do mapa, najwyżywej swojego napisać
  
main(Args) -> 
    L = lists:map(fun(X) -> list_to_integer(X) end, Args),
    io:format("~w\n", [mergesort(L)]).

mergesort([]) -> [];
mergesort([X]) -> [X];
mergesort(L) when is_list(L) ->
    {A, B} = split(L),
    merge(mergesort(A), mergesort(B)).
  
split(L) when is_list(L) -> split(L, [], []).
  
split([], A, B) -> {A, B};
split([X], A, B) -> {[X|A], B};
split([X,Y|T], A, B) -> split(T, [X|A], [Y|B]).
  
merge([], X) -> X;
merge(X, []) -> X;
merge([X1|T1], [X2|T2]) ->
    if
        X1 < X2 -> [X1 | merge(T1, [X2|T2])];
        true    -> [X2 | merge([X1|T1], T2)]
    end.
</file> 
{{tag>[listy_zadan]}}