User:Echo Nolan/Reactive Banana: Straight to the Point

Introduction

So I'm writing this tutorial as a means of teaching myself FRP and reactive-banana. It'll probably be full of errors and bad advice, use it at your own risk.

All the tutorials on FRP I've read start with a long boring theory section. This is an instant gratification article. For starters, imagine a man attempting to sharpen a banana into a deadly weapon. See? You're gratified already! Now for a boring bit:

Go install mplayer: <code-bash>apt-get install mplayer # Or equivalent</code-bash>

Get the git repository associated with this tutorial: <code-bash>git clone https://github.com/enolan/rbsttp.git </code-bash>

Install reactive-banana <code-bash> cabal install reactive-banana</code-bash>

Musical interlude

Cd into the git repo and open rbsttp.hs in GHCi:

<pre-bash> cd rbsttp ghci rbsttp.hs </pre-bash>

Now, we can make some beepy noises. Try these:

<pre-haskell> playNote C2 playNote C6 sequence_ . intersperse (threadDelay 1000000) $ map playNote [C2 ..] </pre-haskell>

Play with the value passed to threadDelay a bit for some more interesting noises. It's expresssed in microseconds.

<pre-haskell> sequence_ . intersperse (threadDelay 500000) $ map playNote [C2 ..] sequence_ . intersperse (threadDelay 250000) $ map playNote [C2 ..] sequence_ . intersperse (threadDelay 125000) $ map playNote [C2 ..] sequence_ . intersperse (threadDelay 62500) $ map playNote [C2 ..] </pre-haskell>

You've probably figured out by now that C2 and C6 are data constructors. Here's the definition for my Note type.

<pre-haskell> data Note = C2 | C3 | C4 | C5 | C6 deriving (Show, Enum) </pre-haskell>