Learn Scala with the koans
You'll need to install a JDK (to run the Scala compiler) and SBT (to download the Scala compiler and library dependencies).
Your meditation session will be assisted by SBT, an excellent tool for interactive Scala development.
- Open a new terminal
- Get this code with
git clone https://github.com/dcecile/scala-koans.git - Go into the new directory (
cd scala-koans) - Start SBT using
sbt namaste - Read the meditation message
- Open the indicated source file and try solve the koan
- Go to step 5
You can exit SBT at any time, and your meditation will automatically resume from where you left off last.
Here are all the koans included in this repository:
| Use... | to meditate on... |
| AboutAsserts | How Scala koans work |
| AboutValAndVar | How val and var declarations differ |
| AboutClasses | How to specify class arguments and fields |
| AboutRange | How to use a convenient class for generating sequences |
| AboutLiteralBooleans | How to specify boolean values |
| AboutLiteralNumbers | How to specify values for the common numeric data types |
| AboutLiteralStrings | How to write literal values for character and string data |
| About Tuples | How to use a convenient class for unnamed structures |
| AboutTuples | How to write a literal tuple value |
| How to access the values in a tuple | |
| Whether all values in a tuple must have the same type | |
| AboutLists | How Nil lists compare |
| How to write a literal list | |
| How to access the values in a list | |
| How to alter the contents of a list | |
| Discovering some common List methods | |
| Transforming, filtering, and summarizing lists | |
| Quickly creating a list of consecutive integers | |
| Sharing content between lists | |
| AboutMaps | How to write a literal map |
| What happens if a key appears more than once | |
| Iterating through the contents of a map | |
| Whether all keys or values in a map must have the same type | |
| How to access the values in a map | |
| How to remove entries from a map | |
| AboutSets | How to write a literal set value |
| What happens if a value appears more than once | |
| Whether all values in a set must have the same type | |
| How to test for the presence of a value in a set | |
| How to alter the content of a set | |
| How to iterate through the values in a set | |
| How to perform familiar operations on a set | |
| AboutMutableMaps | How to create maps whose contents can be altered |
| How to add and remove map content | |
| AboutMutableSets | How to create sets whose contents can be altered |
| How to add and remove set content | |
| AboutFormatting | How to use character literals and escaped sequences |
| AboutPatternMatching | How to use pattern matching to replace complex conditional logic |
| How to ignore part of the data being pattern matched | |
| How to "capture" matched data for later use | |
| How to use pattern matching to simplify working with regular expressions | |
| How to refer to the contents of existing variables when pattern matching | |
| AboutCaseClasses | How to use case classes to write less boilerplate |
| Discovering which methods are automatically provided with case classes | |
| How to create a mutable case class | |
| How to avoid using a mutable case class | |
| How to use named parameters to simplify working with case classes even further | |
| How to "deconstruct"" an instance of a case class | |
| AboutOptions | How to avoid using raw nulls |
| How to safely deal with "missing" or optional data | |
| How to operate on an optional value | |
| How to work with a list of optional values | |
| AboutSequencesAndArrays | How to write a literal array value |
| How to convert between various kinds of sequences | |
| How to transform and filter lists | |
| AboutNamedAndDefaultArguments | How to specify defaults for parameters and how to specify arguments in any order by using names |
| AboutForExpressions | How to iterate sequences, create Ranges, use guards, and nest |
| AboutEmptyValues | How to use None, Some, and Option |
| AboutParentClasses | How to use classes for inheritances and how to use abstract classes |
| AboutTypeSignatures | How to specify generics |
| AboutTraits | How to create self-contained definitions that can be combined with inheritance |
| AboutPreconditions | How to ensure that conditions are met |
| AboutUniformAccessPrinciple | How to interchangeably use fields and methods to hide implementation details |
| AboutHigherOrderFunctions | How to write and use anonymous functions |
| How a closure differs from a "pure" function | |
| How to return a function as a result | |
| How to compose new functions from existing ones | |
| How to use currying to "specialize" functions | |
| How to create a function from a class method | |
| AboutPartialFunctions | How to safely create functions that are only defined for subsets of their arguments |
| How to easily combine these partial functions to create new functions | |
| AboutPartiallyAppliedFunctions | How to create a function by specifying only some of the arguments to another function |
| About Iterables | How to do fun stuff with basic Scala collections while affecting state |
| About Traversables | How to do fun stuff with basic Scala collections without affecting state |
| AboutInfixPrefixAndPostfixOperators | How to know what the compiler is doing with your expressions |
| AboutInfixTypes | How to make expressions read nicely |
| AboutImplicits | How to add to the language to improve readability |
| AboutInteroperability | How to work with Java classes |
| AboutManifests | How to provide meta information about classes |
| AboutEnumerations | How to create and generated values, access index and name, and how to create your own |
| AboutConstructors | How to create auxiliary constructors |
| AboutImportsAndPackages | How to declare packages of your own and how to import other packages |
If you're curious about where these koans came from, you can take a look at these links: