anthonyl
Pipe to Complex Map
I need to do the following:
- Read data from file
- Parse custom syntax
- Write result to a map
I have the following code:
File.stream!(load_path,[:read, :utf8]) #Read File
|> Stream.map(&String.trim(&1)) #Trim Each Element
|> Stream.map(&String.downcase(&1)) #Convert to Lowercase
|> Stream.map(&String.split(&1, [":", ","])) #Split at Delimiters
|> Stream.map(&Map.put(%{}, create_index_name(hd(&1)), tl(&1))) #Write to Map
|> Enum.map(&IO.inspect(&1)) #Enumerate through stream
Which outputs a list with map entries in it like so:
[
%{":jhb_team_names" => ["hawks", "maulers", "eagles", wolves"]},
%{":dbn_team_names" => ["sqeaks", "bunfighters"]}
]
I need it to output something like:
%{":jhb_team_names" => ["hawks", "maulers", "eagles", wolves"],
:dbn_team_names" => ["sqeaks", "bunfighters"]}
i.e. a single map, which can be simply accessed with a key => value lookup.
This should be simple to do, but my newness to Elixir is stumping me.
Any suggestions on how this can be accomplished?
Marked As Solved
dimitarvp
You’ll have to modify part of the code to read the data from a file but otherwise it works. Key insight: use Enum.reduce to accumulate values into a single return value, instead of making a one-keyed map for each parsed line.
defmodule Parse1 do
def data(), do: ~S"""
jhb team names:hawks,maulers,eagles,wolves
dbn team names:sqeaks,bunfighters
"""
def stream_string(text) do
{:ok, io} = StringIO.open(text)
IO.stream(io, :line)
end
def create_index_name(name) do
":" <> String.replace(name, " ", "_")
end
def test() do
# Replace first two lines with your file reading code.
data()
|> stream_string()
|> Stream.map(&String.trim(&1))
|> Stream.map(&String.downcase(&1))
|> Stream.map(&String.split(&1, [":", ","]))
|> Enum.reduce(%{}, fn [head | tail], acc ->
Map.put(acc, create_index_name(head), tail)
end)
end
end
Copy-paste that in iex and then run Parse1.test().
Also Liked
dimitarvp
Can you post some example source data (and possibly the source of create_index_name)? Also, please format your code blocks with triple backticks, right now it’s almost unreadable.
anthonyl
Thx, it works perfectly now!
Also thx for the education to improve my knowledge 
.
gregvaughn
In this case, I wouldn’t even bother with the Stream.map calls. The extra indirection is slowing you down and adding complexity for no real benefit. Thanks to @dimitarvp 's nice sample code, I took it and modified a bit to be more direct.
defmodule Parse2 do
def data(), do: ~S"""
jhb team names:hawks,maulers,eagles,wolves
dbn team names:sqeaks,bunfighters
"""
def stream_string(text) do
{:ok, io} = StringIO.open(text)
IO.stream(io, :line)
end
def create_index_name(name) do
":" <> String.replace(name, " ", "_")
end
def line_to_kv(line) do
[key | names] =
line
|> String.trim()
|> String.downcase()
|> String.split([":", ","])
{create_index_name(key), names}
end
def test2() do
# Replace first two lines with your file reading code.
data()
|> stream_string()
|> Map.new(&line_to_kv/1)
end
end
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