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Codedown is a little utility to extract code blocks from Markdown files.

Inspired by literate Haskell, codedown can be used to:

• Validate the correctness of code embedded in Markdown
• Run code embedded in Markdown
• Ship code and Markdown together in harmony

To skip installing codedown locally, try it online.

Install codedown:

$ npm install -g codedown

Run codedown:

$ codedown
usage: codedown <lang>
ex: codedown haskell

Codedown reads Markdown from stin, extracts the code blocks designated as language <lang>, and outputs them to stdout.

You can pipe the output of codedown to a language interpreter:

$ cat README.md | codedown haskell | runhaskell
42

$ cat README.md | codedown javascript | node
42

$ cat README.md | codedown scala | scala
scala> val x = 42
x: Int = 42
scala> println(x)
42
scala> :quit

This readme is a Markdown file, so we can use codedown to extract code from it.

In the following code blocks, let's set x to 42 in different languages:

Haskell:

x :: Int
x = 42

JavaScript:

var x = 42;

Scala:

val x = 42

Now let's print x it to stdout in different languages.

This time, the code blocks are nested within an unordered list:

• Haskell:

  main :: IO ()
  main = putStrLn $ show x

• JavaScript:

  console.log(x);

• Scala:

  println(x)