Best way to simulate a for loop in Elixir?

Question

Common imperative programming languages provide a loop structure for running a block of code many times? e.g. for loop: pseudo code:

for(i=0;i<256;++i){
  expression one;
  statement one;
  many code goes here
}

The large block of code in the for loop will be executed many times. But as a functional programming langage, Elixir provide no loop. I know Enum module provides many functions for iterating code many times. e.g.

Enum.each(0..99, fn(x) -> IO.puts "hello, world!" end)

The code above will be executed 100 times. Print 100 "hello, world!" But it's just a one-line statement. How to execute a large block of code n times in Elixir? What is the right Elixir way to do so? I'm fresh new to Elixir. Could you guys give me a small sample code for learning? Thank all of you guys so much!

Solution 1

You have a good enough solution right in your question. Enum.each is one bona fide way to apply a function X number of times.

Maybe if we format it differently, you might see what you can do:

Enum.each(0..99, fn(_x) ->
  IO.puts "hello, world!"
end)

The function is just like any other function, except that it is defined inline.

So, just add more lines of code ...

Enum.each(0..99, fn(x) ->
  IO.puts "hello, world!"
  IO.puts x
end)

If you want to reference a defined function, you can pass a function signature:

defmodule Test do

  def bar(x) do
    IO.puts "hello, world!"
    IO.puts x
  end

  def foo do
    Enum.each(0..99, &bar/1)
  end

end

Solution 2

There are many ways of doing it. You can just write your own recursive function or follow other examples mentioned here.

You can also define your "block" of code as a separate function (anonymous or named) and use it in Enum.each or Enum.map depending on what exactly needs to be returned.

Or actually use for like this:

for x <- 0..10 do 
  yor_block_of_code
end

Solution 3

For lazy iteration one might use Stream.iterate/2:

1
|> Stream.iterate(& &1+1)
|> Stream.each(&IO.puts(&1))
|> Enum.take(99)

Comments

[Michael Dimmitt]

I would only add to this Enum.map(0..99, fn(x) -> "hello, world!" end) |> IO.inspect(); Now the side effect is deferred till the end 😉.