CODEWITHSUNDEEP
formaterlangelixir
Marsel.V
Marsel.V

Reputation: 1044

in Elixir: string formatting

I have a transform rule: 

"0549$2"

How do I apply this rule to strings in an Elixir? In ruby i use:

format("0549%2$s", *["88", "77"])
=> "054977"

In Elixir I write:

:io.format("0549%2$s", ["88", "77"])
** (ArgumentError) argument error
    (stdlib) :io.format(#PID<0.54.0>, "0549%2$s", ["88", "77"])

Because :io.format from erlang does not understand this format

Upvotes: 0

Views: 2585

Answers (2)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121010

You might use :io_lib.format/2. It produces the charlist, that can be converted to binary afterwards:

"0549~i~s"
|> :io_lib.format(~w[77 88])
|> to_string()
#⇒ "054988"
  • ~i stays for “ignore the next term”
  • ~s for treating the parameter as a binary

Sidenote: io.format outputs the formatted string to the IO device, returning :ok.

Upvotes: 4

Dogbert
Dogbert

Reputation: 222388

So you want to replace all $ followed by an integer with the corresponding element (indexed from 1) of a list? Here's one way using Regex.replace/3:

defmodule A do
  def format(string, list) do
    Regex.replace(~r/\$(\d+)/, string, fn _, index ->
      Enum.at(list, String.to_integer(index) - 1)
    end)
  end
end

IO.inspect A.format("0549$2", ["88", "77"])
IO.inspect A.format("0549$1", ["88", "77"])

Output:

"054977"
"054988"

Upvotes: 3

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