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Allow Enum.zip/1 and Stream.zip/1 to work on Streams #7219

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jgmchan wants to merge 2 commits into from
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Allow Enum.zip/1 and Stream.zip/1 to work on Streams #7219

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0c3461c
Allow Enum.zip/1 and Stream.zip/1 to work on Streams
jgmchan Jan 18, 2018
feece33
Cannot use `%Stream{}` in pattern matching for `Enum`
jgmchan Jan 18, 2018
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8 changes: 6 additions & 2 deletions lib/elixir/lib/enum.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -2734,11 +2734,15 @@ defmodule Enum do
[{1, :a}, {2, :b}, {3, :c}]

"""
@spec zip([t]) :: t
@spec zip([t] | %Stream{}) :: t

def zip([]), do: []

def zip(enumerables) when is_list(enumerables) do
def zip(%{__struct__: Stream} = enumerables), do: do_zip(enumerables)
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@jgmchan jgmchan Jan 18, 2018

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Used pattern matching for the __struct__ key because clean compilation fails if I use this:

def zip(%Stream{} = enumerables), do: do_zip(enumerables)

I'm wondering if we need to check the enumerable type here if Stream.zip/1 already does it.


def zip(enumerables) when is_list(enumerables), do: do_zip(enumerables)

defp do_zip(enumerables) do
Stream.zip(enumerables).({:cont, []}, &{:cont, [&1 | &2]})
|> elem(1)
|> :lists.reverse()
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8 changes: 6 additions & 2 deletions lib/elixir/lib/stream.ex
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Expand Up @@ -1106,8 +1106,12 @@ defmodule Stream do
[{1, :a, "foo"}, {2, :b, "bar"}, {3, :c, "baz"}]

"""
@spec zip([Enumerable.t()]) :: Enumerable.t()
def zip(enumerables) when is_list(enumerables) do
@spec zip([Enumerable.t()] | %Stream{}) :: Enumerable.t()
def zip(%Stream{} = enumerables), do: zip_fun(enumerables)

def zip(enumerables) when is_list(enumerables), do: zip_fun(enumerables)

defp zip_fun(enumerables) do
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@jgmchan jgmchan Jan 18, 2018

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This is a a pretty bad name but I can't think of a better one 😄 . I thought about calling it _zip but I think it seems to clash with the convention of unimported functions. Any advice on this would be great!

step = &do_zip_step(&1, &2)

enum_funs =
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4 changes: 4 additions & 0 deletions lib/elixir/test/elixir/stream_test.exs
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Expand Up @@ -1084,6 +1084,10 @@ defmodule StreamTest do
assert Stream.zip([concat, cycle]) |> Enum.to_list() ==
[{1, :a}, {2, :b}, {3, :c}, {4, :a}, {5, :b}, {6, :c}]

assert Stream.chunk_every([0, 1, 2, 3], 2)
|> Stream.zip()
|> Enum.to_list() == [{0, 2}, {1, 3}]

assert_raise FunctionClauseError, fn ->
enum_of_enums = Stream.cycle([[1, 2], [:a, :b]])
Stream.zip(enum_of_enums)
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