Given the
{ok, result} | {:error, result}
convention and the beautiful nature of piping, I often find myself looking
for an elegant way to "strain" out all of the {:error _} results in the
middle of a pipe so I can continue processing the results that were
successful. I know the Enum and Stream modules already have a lot of
functions but I think a strain function would add significant value
especially in overall code readability.
Here is a possible source example
def strain(enumerable) do
Enum.reduce(enumerable, [], fn
{:ok, tuple}, acc when is_tuple(tuple) ->
case tuple do
{:ok, result} -> [result | acc]
{:error, _} -> acc
end
{:ok, result}, acc -> [result | acc]
_, acc -> acc
end)
end
And an overloaded version that allows for handling errors:
def strain(enumerable, fun) do
Enum.reduce(enumerable, [], fn
{:ok, tuple}, acc when is_tuple(tuple) ->
case tuple do
{:ok, result} -> [result | acc]
{:error, result} ->
fun.(result)
acc
end
{:ok, result}, acc -> [result | acc]
{:error, result}, acc ->
fun.(result)
acc
_, acc -> acc
end)
end
This would allow client code to look like this:
results = list
|> Enum.map(&do_something/1)
|> Enum.strain()
|> Task.async_stream(&do_another_expensive_thing/1)
|> Enum.strain()
|> Enum.to_list()
Simple examples (for clarity)
iex> Enum.strain([{:ok, "good job"}, {:error, "bad input"}])
["good job"]
iex> Enum.strain([{:error, "bad input"}], &IO.inspect/1)
"bad input"
[]
Thanks,
Spencer Carlson
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