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.rebar3 | ||
_* | ||
.eunit | ||
*.o | ||
*.beam | ||
*.plt | ||
*.swp | ||
*.swo | ||
.erlang.cookie | ||
ebin | ||
log | ||
erl_crash.dump | ||
.rebar | ||
logs | ||
_build |
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language: erlang | ||
otp_release: | ||
- 18.2.1 | ||
- 17.5 |
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The MIT License (MIT) | ||
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Copyright (c) 2016 Yakov | ||
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Permission is hereby granted, free of charge, to any person obtaining a copy | ||
of this software and associated documentation files (the "Software"), to deal | ||
in the Software without restriction, including without limitation the rights | ||
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
copies of the Software, and to permit persons to whom the Software is | ||
furnished to do so, subject to the following conditions: | ||
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The above copyright notice and this permission notice shall be included in all | ||
copies or substantial portions of the Software. | ||
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | ||
SOFTWARE. | ||
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# Erlang zlist: a lazy sequences library. | ||
---------------------------------------------------- | ||
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## Description ## | ||
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Unlike https://github.com/vjache/erlang-zlists | ||
zlist() is a function that returns improper list with data and next zlist or | ||
an empty list. | ||
You can use it to organize lazy evolution or backpressure. | ||
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Simple infinite iterator: | ||
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```erlang | ||
1> SimpleZ = fun Loop() -> [1|Loop] end. | ||
#Fun<erl_eval.44.90072148> | ||
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2> zlist:take(10, SimpleZ). | ||
{[1,1,1,1,1,1,1,1,1,1],#Fun<erl_eval.62.90072148>} | ||
``` | ||
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## Usage ## | ||
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### Integrate to your project ### | ||
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This is a rebar'ized project, so, if you are already using rebar, just insert a reference | ||
to this git repo at your rebar.config. | ||
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### Examples ### | ||
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```erlang | ||
1> Z = zlist:recurrent(fun(A) -> A + 1 end, 0). | ||
#Fun<zlist.14.21462417> | ||
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2> zlist:take(10, Z). | ||
{[1,2,3,4,5,6,7,8,9,10],#Fun<zlist.14.21462417>} | ||
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3> Z2 = zlist:map(fun(A) -> A * 2 end, Z). | ||
#Fun<zlist.3.21462417> | ||
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4> zlist:take(10, Z2). | ||
{[2,4,6,8,10,12,14,16,18,20],#Fun<zlist.3.21462417>} | ||
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5> ZL = zlist:from_list([1,2,5]). | ||
#Fun<zlist.12.21462417> | ||
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6> zlist:to_list(ZL). | ||
[1,2,5] | ||
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7> ZR = zlist:ciclyc(ZL). | ||
#Fun<zlist.17.21462417> | ||
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8> zlist:take(10, ZR). | ||
{[1,2,5,1,2,5,1,2,5,1],#Fun<zlist.17.21462417>} | ||
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9> Z3 = zlist:flatmap(fun(A) -> zlist:from_list([-A, A]) end, Z2). | ||
#Fun<zlist.6.21462417> | ||
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10> zlist:take(10, Z3). | ||
{[-2,2,-4,4,-6,6,-8,8,-10,10],#Fun<zlist.10.21462417>} | ||
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``` | ||
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### Warnings !!! ### | ||
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With zlist you are working with potentially infinite data. | ||
Don't use ```to_list/1```, ```foreach/2```, ```fold/3``` functions | ||
until you know that iterator is finite state. | ||
Use ```dropwhen/1``` before, or ```take/2``` instead. |
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{application, zlist, | ||
[{description, "Erlang lazy list library"}, | ||
{vsn, git}, | ||
{registered, []}, | ||
{applications, | ||
[kernel, | ||
stdlib | ||
]}, | ||
{env,[]}, | ||
{modules, []}, | ||
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{maintainers, ["Yakov Kozlov"]}, | ||
{licenses, ["MIT"]}, | ||
{links, [{"Github", "https://github.com/egobrain/zlist"}]} | ||
]}. |
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-module(zlist). | ||
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-export([ | ||
map/2, | ||
filter/2, | ||
filtermap/2, | ||
flatmap/2, | ||
over/3, | ||
dropwhen/2, | ||
dropwhile/2, | ||
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append/2, | ||
ciclyc/1, | ||
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empty/0, | ||
seq/2, | ||
seq/3, | ||
recurrent/2, | ||
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foreach/2, | ||
fold/3, | ||
take/2, | ||
takewhile/2, | ||
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from_list/1, | ||
to_list/1 | ||
]). | ||
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-type zlist(A) :: fun(() -> maybe_improper_list(A, zlist(A))) | empty_zlist(). | ||
-type empty_zlist() :: fun(() -> []). | ||
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-export_type([ | ||
zlist/1, | ||
empty_zlist/0 | ||
]). | ||
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%% ============================================================================= | ||
%% API functions | ||
%% ============================================================================= | ||
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-spec empty() -> empty_zlist(). | ||
empty() -> fun() -> [] end. | ||
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-spec seq(From, To) -> zlist(integer()) when | ||
From :: integer(), | ||
To :: integer(). | ||
seq(First, Last) when is_integer(First), is_integer(Last), First-1 =< Last -> | ||
seq_(First, Last). | ||
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seq_(Curr, Last) -> | ||
fun() -> | ||
case Curr > Last of | ||
true -> []; | ||
false -> [Curr] ++ seq_(Curr+1, Last) | ||
end | ||
end. | ||
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-spec seq(From, To, Incr) -> zlist(integer()) when | ||
From :: integer(), | ||
To :: integer(), | ||
Incr :: integer(). | ||
seq(First, Last, Inc) when is_integer(First), is_integer(Last), is_integer(Inc) -> | ||
if | ||
Inc > 0, First - Inc =< Last; | ||
Inc < 0, First - Inc >= Last -> | ||
N = (Last - First + Inc) div Inc, | ||
seq_(N, First, Inc); | ||
Inc =:= 0, First =:= Last -> | ||
seq_(1, First, Inc) | ||
end. | ||
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seq_(N, X, D) -> | ||
fun() -> | ||
case N of | ||
0 -> []; | ||
_ -> [X] ++ seq_(N-1, X+D, D) | ||
end | ||
end. | ||
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-spec map(fun((A) -> B), zlist(A)) -> zlist(B). | ||
map(Fun, Zlist) -> | ||
fun() -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
[Fun(Data)] ++ map(Fun, Next); | ||
Done -> Done | ||
end | ||
end. | ||
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-spec foreach(fun((A) -> ok), zlist(A)) -> ok. | ||
foreach(Fun, Zlist) -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
_ = Fun(Data), | ||
foreach(Fun, Next); | ||
_Done -> ok | ||
end. | ||
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-spec filter(fun((A) -> boolean()), zlist(A)) -> zlist(A). | ||
filter(Fun, Zlist) -> | ||
fun() -> | ||
(fun Loop(Z) -> | ||
case Z() of | ||
[Data|Next] -> | ||
case Fun(Data) of | ||
true -> [Data] ++ filter(Fun, Next); | ||
false -> Loop(Next) | ||
end; | ||
Done -> Done | ||
end | ||
end)(Zlist) | ||
end. | ||
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-spec filtermap(fun((A) -> {true, B} | false), zlist(A)) -> zlist(B). | ||
filtermap(Fun, Zlist) -> | ||
fun() -> | ||
(fun Loop(Z) -> | ||
case Z() of | ||
[Data|Next] -> | ||
case Fun(Data) of | ||
{true, Data2} -> [Data2] ++ filtermap(Fun, Next); | ||
false -> Loop(Next) | ||
end; | ||
Done -> Done | ||
end | ||
end)(Zlist) | ||
end. | ||
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-spec fold(fun((A, S) -> S), S, zlist(A)) -> S. | ||
fold(Fun, State, Zlist) -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
fold(Fun, Fun(Data, State), Next); | ||
_Done -> State | ||
end. | ||
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-spec flatmap(fun((A) -> zlist(B)), zlist(A)) -> zlist(B). | ||
flatmap(Fun, Zlist) -> | ||
fun() -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
(append(Fun(Data), flatmap(Fun, Next)))(); | ||
Done -> Done | ||
end | ||
end. | ||
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-spec over(fun((A,S) -> {B, S}), S, zlist(A)) -> zlist(B). | ||
over(Fun, S, Zlist) -> | ||
fun() -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
{Value, S2} = Fun(Data, S), | ||
[Value] ++ over(Fun, S2, Next); | ||
Done -> Done | ||
end | ||
end. | ||
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-spec dropwhen(fun((A) -> boolean()), zlist(A)) -> zlist(A). | ||
dropwhen(Fun, Zlist) -> | ||
fun() -> | ||
case Zlist() of | ||
[Data|Next] -> | ||
case Fun(Data) of | ||
true -> []; | ||
false -> [Data] ++ dropwhen(Fun, Next) | ||
end; | ||
Done -> Done | ||
end | ||
end. | ||
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-spec dropwhile(fun((A) -> boolean()), zlist(A)) -> zlist(A). | ||
dropwhile(Fun, Zlist) -> | ||
fun() -> | ||
(fun Loop(Z) -> | ||
case Z() of | ||
[Data|Next]=R -> | ||
case Fun(Data) of | ||
true -> Loop(Next); | ||
false -> R | ||
end; | ||
Done -> Done | ||
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end | ||
end)(Zlist) | ||
end. | ||
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-spec append(zlist(A), zlist(B)) -> zlist(A|B). | ||
append(Zlist1, Zlist2) -> | ||
fun() -> | ||
case Zlist1() of | ||
[Data|Next] -> [Data] ++ append(Next, Zlist2); | ||
_Done -> Zlist2() | ||
end | ||
end. | ||
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-spec ciclyc(zlist(A)) -> zlist(A). | ||
ciclyc(Zlist) -> | ||
(fun Loop(Z) -> | ||
fun() -> | ||
case Z() of | ||
[Data|Next] -> [Data] ++ Loop(Next); | ||
_Done -> (ciclyc(Zlist))() | ||
end | ||
end | ||
end)(Zlist). | ||
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-spec from_list([A]) -> zlist(A). | ||
from_list(List) -> | ||
fun() -> | ||
case List of | ||
[H|T] -> [H] ++ from_list(T); | ||
_ -> List | ||
end | ||
end. | ||
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-spec to_list(zlist(A)) -> [A]. | ||
to_list(Zlist) -> lists:reverse(fold(fun(H, T) -> [H|T] end, [], Zlist)). | ||
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-spec recurrent(fun((A) -> A), A) -> zlist(A). | ||
recurrent(Fun, S) -> | ||
fun() -> | ||
Next = Fun(S), | ||
[Next] ++ recurrent(Fun, Next) | ||
end. | ||
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-spec take(N :: pos_integer(), zlist(A)) -> {[A], zlist(A)}. | ||
take(N, Zlist) when N > 0 -> | ||
take_(N, [], Zlist). | ||
take_(0, Acc, Z) -> {lists:reverse(Acc), Z}; | ||
take_(C, Acc, Z) -> | ||
case Z() of | ||
[Data|Next] -> take_(C-1, [Data|Acc], Next); | ||
_Done -> {lists:reverse(Acc), empty()} | ||
end. | ||
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-spec takewhile(fun((A) -> boolean()), zlist(A)) -> {[A], zlist(A)}. | ||
takewhile(Fun, Zlist) -> takewhile_(Fun, [], Zlist). | ||
takewhile_(Fun, Acc, Z) -> | ||
case Z() of | ||
[Data|Next] = R -> | ||
case Fun(Data) of | ||
true -> takewhile_(Fun, [Data|Acc], Next); | ||
false -> {lists:reverse(Acc), fun() -> R end} | ||
end; | ||
_Done -> {lists:reverse(Acc), empty()} | ||
end. |
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[]. |
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