Jayshua
How to end for comprehension early
I’m trying to figure out how to use Elixir’s version of for comprehensions.
The Phoenix live view generator creates this code in the live/page_live.ex file to get the search results:
for {app, desc, vsn} <- Application.started_applications(),
app = to_string(app),
String.starts_with?(app, query) and not List.starts_with?(desc, ~c"ERTS"),
into: %{},
do: {app, vsn}
How could I go about making this return at most 5 results? I tried using Enum.with_index on the first line and adding an index < 5 filter, but that just limited the search space to the first 5 dependencies.
Marked As Solved
mudasobwa
for comprehension is greedy, so it would pass through the whole list no matter what.
Some time ago I have implemented lazy comprehension with LazyFor having nearly the same syntax as for (but it’s somewhat limited yet.)
iex|1 ▶ import LazyFor
iex|2 ▶ stream {app, desc, vsn} <- Application.started_applications(),
...|2 ▶ app = to_string(app),
...|2 ▶ String.starts_with?(app, "") and not List.starts_with?(desc, ~c"ERTS"),
...|2 ▶ take: 5, # THIS
...|2 ▶ do: {app, vsn}
[
{"lazy_for", '0.3.0'},
{"benchfella", '0.3.5'},
{"hex", '0.20.5'},
{"inets", '7.1.2'},
{"ssl", '9.6'}
]```Popular in Questions
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