Anko
Ordered sorting of a map to a keyword list
Just wondered if there is some standard library function for converting a map to a keyword list, but sorting it on the way.
something like;
map = %{"z" => 4, "y" => 6, "x" => 7}
order = ["x", "y"]
output = new_func(map, order)
# output now equals [{"x", 7}, {"y", 6}]
Marked As Solved
codeanpeace
Here’s one approach:
iex(1)> map = %{"z" => 4, "y" => 6, "x" => 7}
%{"x" => 7, "y" => 6, "z" => 4}
iex(2)> order = ["x", "y"]
["x", "y"]
iex(3)> Enum.map(order, fn key -> {key, Map.get(map, key)} end)
[{"x", 7}, {"y", 6}]
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dimitarvp
No the stdlib does not have that and you’ll see exactly why: it’s easy to do it yourself.
%{"z" => 4, "y" => 6, "x" => 7}
|> Map.take(["x", "y"]) # only take keys "x" and "y"
|> Map.to_list() # convert the map to a list of tuples
|> Enum.sort_by(fn {key, _value} -> key end) # sort the list of tuples by their first element
And you will get [{"x", 7}, {"y", 6}] as your result.
adamu
(actually 
).
dimitarvp
Last Post!
adamu
I didn’t benchmark it, but it’s nlogn, which is about par for the course for sorting in immutable languages AFAIK. Premature optimisation, etc…
Let’s not discuss further if nobody’s willing to actually run the numbers 
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