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-module(zf).
-compile(export_all).
%% Odd numbers.
%%foo(L) -> [ X || X <- L, (X > X-1) == (X /= X-1) ].
boo() -> [X||X <- [1,2,a,3,4,b,5,6], X > 3].
boo1() -> [X||X <- [1,2,a,3,4,b,5,6], integer(X),X > 3].
boo2() -> [{X,Y} || X <- [1,2,3], Y <- [a,b]].
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.
%% 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(A,B) ->
[ {X,Y} ||
X <- A,
Y <- B
].
%% 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([]) -> [].
%% append
append(L) -> [X||L1<-L,X<-L1].
map(Fun, L) -> [Fun(X)||X<-L].
filter(Pred, L) -> [X||X<-L,Pred(X)].
select(X, L) -> [Y || {X1,Y} <- L, X == X1].
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