Rich_Morin
Formatting a list of strings - am I missing anything?
I recently wrote some Elixir to format a list of strings (eg, author names) for output. I think it’s reasonably idiomatic, but I probably missed a few tricks. Suggestions, anyone?
-r
It should work like this…
iex(0)> list_str []
""
iex(1)> list_str [1]
1
iex(2)> list_str [1,2]
"1 and 2"
iex(3)> list_str [1,2,3]
"1, 2, and 3"
And now, the code… (ducks)
@doc """
Join a list of strings into a (mostly) comma-delimited string.
"""
def list_str( [] ), do: ""
def list_str( [ one ] ), do: one
def list_str( [ one, two ] ), do: "#{ one } and #{ two }"
def list_str(inp_list) do
[ last | base_list ] = Enum.reverse(inp_list)
base_str = base_list
|> Enum.reverse()
|> Enum.join(", ")
"#{ base_str }, and #{ last }"
end
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blatyo
Should probably be:
def list_str( [ one ] ), do: to_string(one)
Otherwise, looks fine to me.
blatyo
They should be the same. I personally tend to use to_string instead of interpolation, when it’s only the value that I’m converting to a string. I’d use interpolation when I want to convert the values to a string and concatenate with something else.
peerreynders
When it comes to serial commas the comma before the “and” is optional - it just can’t be there if you have less than three items.
So I guess recursion isn’t idiomatic?
def list_str([]),
do: ""
def list_str([one]),
do: to_string(one)
def list_str(list),
do: list_str(list, [])
defp list_str([], [h, n | t]),
do: list_to_str(t, to_string(n) <> " and " <> to_string(h))
defp list_str([h | t], rest),
do: list_str(t, [h | rest])
defp list_to_str([], str),
do: str
defp list_to_str([h | t], str),
do: list_to_str(t, to_string(h) <> ", " <> str)
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