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fix example comment in Enum.slide/3 #13779

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Merged
merged 2 commits into from
Aug 14, 2024
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fix example comment in Enum.slide/3 #13779

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53263b5
fix example comment in Enum.slide/3
davidsulc Aug 14, 2024
77359ae
reword to reduce ambiguity
davidsulc Aug 14, 2024
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4 changes: 2 additions & 2 deletions lib/elixir/lib/enum.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -2706,11 +2706,11 @@ defmodule Enum do
iex> Enum.slide([:a, :b, :c, :d, :e, :f, :g], 5, 1)
[:a, :f, :b, :c, :d, :e, :g]

# Slide a range of elements backward
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Both interpretations can be right, but semantically, it is forward, because we are bringing the elements from 3..5 to position 1 (and as a result, the ones from 1..2 are brought forward, but the ones we specify go back).

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the ones we specify go back

Could you expand on that a little? Which elements are "the ones we specify" and what do you mean by "go back"?

I'd interpret the elements we specify as the 3..5 slice, i.e. elements [:d, :e, :f]. Originally, these elements are in positions 3-5, but after the slide/3 call, they are in positions 1-3. As these elements have moved towards the head of the list, wouldn't this be "going forward"?

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Oh, I see where the confusion is coming from, it is about what is forward, the head or the tail? What if instead of forwards and backwards and we say "towards the head" and "towards the tail"?

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That was indeed the source of my confusion: "forward" being "in the reading direction" vs "toward the list head". I've reworded the change to remove ambiguity. Thanks for clarifying your meaning!

# Slide a range of elements forward
iex> Enum.slide([:a, :b, :c, :d, :e, :f, :g], 3..5, 1)
[:a, :d, :e, :f, :b, :c, :g]

# Slide a range of elements forward
# Slide a range of elements backward
iex> Enum.slide([:a, :b, :c, :d, :e, :f, :g], 1..3, 5)
[:a, :e, :f, :b, :c, :d, :g]

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