Many DSLs start as libraries or APIs, and a first-draft library is a low-cost way to experiment with language design. In this lab, we'll do a first-draft design of a sound-processing library. The goal is to get practice writing a fluent library, that is: a library that makes it easier and more natural for its users to accomplish specific tasks.

This lab revisits one that was created for CS 5. In CS 5, the goal was to learn about Python's functional programming capabilities, including:

• lists
• list comprehensions
• map, filter, reduce
• function definitions and calls

In DSLs, our goal is to use those features to design a nice library.

1. Fork this repository, which contains all the Python and sound files you'll need.

2. Submit a pull request right away. (The pull request will be updated as you work on the lab.)

3. Head over to the CS 5 writeup. Take a brief look at the top of the file, to see a description of the files. (You won't need to download the files though; they're already included in your fork.)

4. Skim / skip down to the section titled "Sound coding...". Start doing the lab from there. (The earlier part of the lab, which creates some helper function has already been completed in the hw3pr1.py file that comes with this repository.)

Our goals are a bit different from the Python lab. If you follow the instructions in the lab, you'll find that you create a library that's not as easy to use as we'd like. You're goal is to improve on the design.

In particular, focus on the following:

• Make it easier for a user of the library to combine multiple sound effects in a single file.

• As much as possible, try to use a limited set of tools to create your library. In particular, reach first for the language features mentioned at the top of this lab. If those tools don't seem up for the job, then you can reach for other tools (e.g., for loops, classes, etc.).

• As an initial goal, it should be easy for users of your library to:

  1. Modify an existing sound file by reversing it and making it quieter.
  2. Play the resulting sound.
  3. Save that sound to a file.

• After that, it should be easy to similarly combine any number of effects and either play or save the resulting sound.

• As a stretch goal, see if you can make it easy for a library user to compose a song of arbitrary sounds. This information about sound frequencies may help. If you're looking for a test song, here are the notes for Twinkle, twinkle, little star:

   A A E E F# F# E
   D D C# C# B B A
   E E D D C# C# B
   E E D D C# C# B
   A A E E F# F# E
   D D C# C# B B A