CODEWITHSUNDEEP
elixir
chx
chx

Reputation: 11760

How to create a map from a comprehension?

I tried

units = %{}
for s <- squares, u <- unitlist, s in u, do: Map.put(units, s, u)

which doesn't seem to work. I would like to create a map where the keys are in squares the values are in unitlist and the map should only contains those squares which are in the unitlist.

Ultimately, I'd like something like

units = for s <- squares, u <- unitlist, s in u, ????

Upvotes: 1

Views: 623

Answers (1)

Dogbert
Dogbert

Reputation: 222118

which works

That code will not work like you probably expect it to. What it does is create a new Map on every iteration, but the units map declared before will not be modified because variables in Elixir are immutable.

You can use the into option with for to create a map. For that, the body of the loop must return a 2-tuple of the key and value.

units = for s <- squares, u <- unitlist, s in u, into: %{}, do: {s, u}

Upvotes: 3

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