Basic Data Structures

My Take on UCSD's Basic Data Structures course (CSE 12)

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How to use Other People’s Code

An Introduction to Libraries

All quarter, we’ve implemented our own takes on a lot of data structures.

Most times, it is advisable not to create your own, instead opting for a library implementation.

Today, we’ll cover how to use different libraries in C++, as well as talk a bit about other languages’ libraries.

Libraries

Nearly every language has some sort of standard library. Here are a few examples:

• C
  • libc
• C++
  • C++ standard template library (STL)
• Java
  • Java Standard Library
• Python
  • Python Standard Library
• Rust
  • Rust Standard Library
• Haskell
  • Hoogle
• OCaml
  • OCaml Standard Library

Most languages also include specialty libraries for things like GUI development, databases, web development, and more.

Here is a step-by-step guide to using libraries:

1. Formalize the problem that you want to solve
   • Are you trying to build a web app? Do you need to do something involving multithreading?
   • By asking yourself what your objective is, you can better search for the library you need.
2. Search for a library that matches what you want
   • GitHub, Stack Overflow, forum posts, and more can help you track down the right library for your project.
3. Figure out how to install
   • Does your library come preinstalled? Do you need to use a package manager (e.g. pip, cargo, homebrew, etc)?
   • You cannot use a library unless you know how to get it on your machine!
4. Figure out how to import it into your code
   • Is it a C/C++ header file that you include with a #include directive?
     • Note for these: you usually have to compile with the -I flag in your compiler to use a separate include path
   • Is it a Java package you need to add to your -classpath?
   • Does your language have special import syntax?
5. Read the documentation to see how best to use the code
   • Often, the documentation comes with examples on how to use the library best!
6. Use the library
   • Use this library to solve your problem!
7. Figure out how to compile/run your code
   • You may need new compiler options or may need to tweak your runtime configuration to allow for new libraries.
8. Figure out how to package up your code optional: needed if creating an app
   • If you want other people to use your code, you’ll need them to be able to run it the same as you.
   • Maybe your language of choice has a packaging system (like Java’s JAR format), or maybe you can create install scripts!

Example: C++ boost

The boost C++ library is a large, open-source project providing TONS of things to C++ that aren’t already there.

Some features from boost have become popular enough to be adapted into the main C++ STL!

We will now show an example of how to use boost for a non-trivial project (that you will implement from scratch in CSE 100): Six Degrees of Kevin Bacon

1. Formalize the problem
   • At its core, the problem boils down to a graph search. If each actor is a node, we want to find the “Bacon number” (i.e. number of hops to Kevin Bacon) for each one.
2. Search for a library
   • Conviently, boost has a section titled the Boost Graph Library which can help us with this task.
3. Figure out how to install
   • On macOS, we can use Homebrew by typing brew install boost
4. Figure out how to import
   • Since boost is a C++ header only library, we don’t have to do any custom builds. All we need to do is add an include statement, and add it to our buildpath when compiling.
5. Read the documentation
   • Here it is!
6. Use the library
   • Instead of subjecting you to watching me type, I’ve instead linked to a completed project for this.
   • You can find it here!
7. Figure out how to compile
   • This is given in the Makefile for this project!

That’s all folks! Next time, we begin our review.

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