How to print alphabet in Elixir? (aa ab ac etc)

Questions / Help
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21

sweetness!

1 Like
22

Also, for comprehensions offer binary generators

iex(15)> alphabet = "abcdefghijklmnopqrstuvwxyz"
"abcdefghijklmnopqrstuvwxyz"
iex(16)> for <<x <- alphabet>>, do: <<"a", x>>
["aa", "ab", "ac", "ad", "ae", "af", "ag", "ah", "ai", "aj", "ak", "al", "am",
 "an", "ao", "ap", "aq", "ar", "as", "at", "au", "av", "aw", "ax", "ay", "az"]
8 Likes
23

for example here <<Enum.random(?A..?Z)>> it works, but on my other example when I try to use <<>> it doesnt fix it

24

You should take these posts as hints what to look into, but maybe not start with binary generators just yet.

3 Likes
25

well yea hard coding the alphabet isnt a problem but imagine having a list of like 500 letters or something, hmm

26

Excel encodes the columns in the general pattern of what you need.

In Elixlsx you can find the utility function encode_col that implements the general case (see here):

  def encode_col(0), do: ""
  def encode_col(num) when num <= 26, do: <<num + 64>>

  def encode_col(num, suffix \\ "")
  def encode_col(num, suffix) when num <= 26, do: <<num + 64>> <> suffix

  def encode_col(num, suffix) do
    mod = div(num, 26)
    rem = rem(num, 26)

    if rem == 0 do
      encode_col(mod - 1, "Z" <> suffix)
    else
      encode_col(mod, <<rem + 64>> <> suffix)
    end
  end

Your alphabet would start at encode_col(27)

Edit: you would need to lowercase the string (or adapt the code)

1 Like
27

TIL…

1 Like
28

"a#{letter}" != "a#{[&1]}"

In this case the &1 is equivalent to letter, so that is not the meaningful difference. The difference is wrapping the letter in a list such that the compiler sees it as a charlist. Interpolating a charlist is different than interpolating an integer (which is what letter actually is when you pull it from a charlist).

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