| The selling point for me to get into Haskell was how much better it's lowest bar is than pretty much every other language I've used so far. It's not perfect but it has a very good effort to power ratio. For example, I have a database with millions of unstructured, schemaless JSON documents. The documents are mostly similar but the schema is defined by Javascript code that has been maintained and modified for many, many years and so the documents have many, many edge-cases. I've dared my team to write a JSON-Schema document that could validate our format. It would take a lot of effort to get that going. And it would be verbose and hard to work with: JSON-Schema itself is written in JSON and there exists no tool that can understand the types in the schema, validate them, etc until you run the program on some documents. Instead I spent a few hours and wrote a type that loosely described some of the more common types I've come across in Haskell. I used the wonderful JSON libraries to parse documents from our database using my small, limited type in a test suite. It failed initially but the type system pointed out where it was failing and why. So I added more cases to my type, improved the parser, until I could parse a handful of real-world examples. From there I wrote a tool that scans the whole database, collects the parse results, and displays the top N parse failures with example documents to add to my test suite. I use the test suite to interrogate the parse results, add more cases to my type, extend the parser, etc, etc... I've spent very little time working on this and got my tool successfully parsing almost 90% of the database. When I add new examples the type checker guides me as I interrogate the new case, fix the edge cases, and get the tests to pass. Once I can parse 100% of this database I can start writing a tool to migrate my messy data structure into a more clean, consistent one with a more simple parser and prove that the migration is total. And I suspect it will take even less effort to do that. I'm not even leveraging anything more advanced than ADTs, type classes, and functions. For very little effort Haskell has given me the ability to solve valuable problems. Problems that scared other developers away using other languages. |