-module(t).
-author('[email protected]').
%%-export([test/2]).
-compile(export_all).
%% Odd numbers.
%%foo(L) -> [ X || X <- L, (X > X-1) == (X /= X-1) ].
bar(L) -> [ X || X <- L, integer(X), gt(X, 3) ].
bar(L, M) -> [ Y || X <- L, integer(X), gt(X, 3),
Y <- M, float(Y), gt(X, Y)
].
baz(L) -> [ X || X <- L, atom(X) ].
buz(L, Min) -> [ X || Min > 3, X <- L, X >= Min ].
gt(X, Y) when X > Y -> true;
gt(X, Y) -> false.
%% Turn a list into a set.
make_set([]) -> [];
make_set([H|T]) ->
[H|[
Y || Y <- make_set(T),
Y =/= H
]].
%% Return the Pythagorean triangles with sides
%% of total length less than N
pyth(N) ->
[ {A,B,C} ||
A <- lists:seq(1,N),
B <- lists:seq(1,N),
C <- lists:seq(1,N),
A+B+C =< N,
A*A+B*B == C*C
].
%% Cut the search space a bit..
pyth2(N) ->
[ {A,B,C} ||
A <- lists:seq(1,N),
B <- lists:seq(1,N-A+1),
C <- lists:seq(1,N-A-B+2),
A+B+C =< N,
A*A+B*B == C*C ].
%% Return the Cartesian product
cp() ->
[ {X,Y} ||
X <- a(),
Y <- b()
].
cp(A,B) when list(A),list(B) ->
[ {X,Y} ||
X <- A,
Y <- B
].
%a() -> 1/0.
a() -> [a,b].
b() -> [1,2,3].
%% Return all permutations of a list
perms([]) -> [[]];
perms(L) -> [ [H|T] || H <- L, T <- perms(L--[H]) ].
%% Quick sort
sort([X|Xs]) ->
sort([ Y || Y <- Xs, Y < X ]) ++
[X] ++
sort([ Y || Y <- Xs, Y >= X ]);
sort([]) -> [].
%% Vector addition
vecAdd(Xs,Ys) ->
[ X+Y || {X,Y} <- zip(Xs,Ys) ].
zip([X|Xs],[Y|Ys]) -> [{X,Y}|zip(Xs,Ys)];
zip([],[]) -> [].
qsort([X|Xs]) ->
qsort(lt(X,Xs))
++ [X] ++
qsort(ge(X,Xs));
qsort([]) -> [].
lt(X,[H|T]) when X>H -> [H|lt(X,T)];
lt(X,[_|T]) -> lt(X,T);
lt(_,[]) -> [].
ge(X,[H|T]) when X=<H -> [H|ge(X,T)];
ge(X,[_|T]) -> ge(X,T);
ge(_,[]) -> [].
test(1,N) -> statistics(runtime),test1(N),statistics(runtime);
test(2,N) -> statistics(runtime),test2(N),statistics(runtime);
test(3,N) -> statistics(runtime),test3(N),statistics(runtime).
test1(0) -> true;
test1(N) ->
sort([21,12,45,1,3,87,55,77,11,20,6,99,91,13,14,15,66,62,69,71,67,82,83,84,87,86,85]),
test1(N-1).
test2(0) -> true;
test2(N) ->
qsort([21,12,45,1,3,87,55,77,11,20,6,99,91,13,14,15,66,62,69,71,67,82,83,84,87,86,85]),
test2(N-1).
test3(0) -> true;
test3(N) ->
lists:sort([21,12,45,1,3,87,55,77,11,20,6,99,91,13,14,15,66,62,69,71,67,82,83,84,87,86,85]),
test3(N-1).
