In the few years since Ruby Koans first came out, the approach has been mimicked in a wide variety of programming languages. Work on Haskell Koans was started in January 2012 by Román González and Tatsuhiro Ujihisa.
The premise is simple: A koan is a small snippet of almost-correct code, given for "meditation". Each koan is a kind of puzzle, and is a great way for users to learn more about a language.
Here's a simple example:
import Test.HUnit check p = do assert p putStrLn "OK" --show result = fixMe main = check (2 + 2 == result)
Running this as-is gives a compile error, since
fixMe is undefined. But changing the code by replacing
4 gives a reassuring
OK. You can edit the above code in place before executing it. Go try it!
A lot of programmers are "hands-on" learners, and would rather just try out a new tool and explore some possibilities, rather than starting with a thorough review of documentation or associated research papers.
Building koans on School of Haskell is easy. Here's the markdown behind the above example:
```active haskell import Test.HUnit check p = do assert p putStrLn "OK" --show result = fixMe main = check (2 + 2 == result) ```
The code before
--show is hidden, and has two parts:
- First we
import Test.HUnit, a Haskell unit-testing framework.
- Next we define
check, a thin wrapper around HUnit's
So in general, each koan can look like this:
```active haskell import Test.HUnit check p = do assert p putStrLn "OK" --show YOUR KOAN HERE ```
That's really all there is to it. Koans are a great fit with our Active Haskell, and we'd especially love to see how this approach can be used to introduce users to new libraries. Let us know what you think!
Want to discuss this? Check out our forums!