battermann / parser-combinators-scala-hands-on

A series of exercises on functional parsers

A Hands On Functional Parsers In Scala

A hands on functional parsers in Scala based on "Programming in Haskell" by Graham Hutton.

Prerequisites

• Install Ammonite

How To

This repo has two branches, exercises and solutions.

Checkout the exercises branch and run the tests with amm -w test.sc.

You should get an output similar to this:

tests$ParserTests:
- fail should always fail
- succeed should always succeed with the result value v (pending)
- anyChar should succeed with first char for non empty inputs (pending)
- anyChar should fail if input is empty (pending)
- sequencing (pending)
…

Now, take look at the tests in tests.sc. Here is an example:

property("fail should always fail") {
  pending
  forAll { (input: String) =>
    parser.fail(input) should ===(None)
  }
}

• Go from top to bottom
• Remove the line which says pending from the first pending test
• This should usually make the test fail (red)
• Now implement the function under test (in parser.sc and expr_parser.sc) and try to make the test pass (green)
• Think about if you can improve your implementation (refactor)
• Work through the tests from top to bottom until all tests pass