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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
commit84adefa331c4159d432d22840663c38f155cd4c1 (patch)
treebff9a9c66adda4df2106dfd0e5c053ab182a12bd /system/doc/extensions/list_comrehensions.erl
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The R13B03 release.OTP_R13B03
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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].