Recently, I had to opportunity to help J. The data from them tells how much people and organizations have contributed to various candidates, PAC, and other groups. To get an idea of what the data looks like, you can see a sample of rows from this data file in this Google Sheet. This is a functionalstatically typed programming language with a partially deserved reputation for being difficult.
However, I find that it gives me a nice balance of safety and flexibility, of power and expressiveness. Hopefully this post will prove this at least partially correct and will highlight some of the nicer aspects of working in Haskell.
It leverages types to provide Validating data type in java assurances that the data is well-formed and consistent.
This means I can perform data validation quickly and easily, and that helps everyone. This post is actually runnable Haskell. If you have the GHC compiler installed you can copy and Validating data type in java this post into a file, say Validating. To validate the data, we just need to follow the same steps that we would to load it.
Basically, they specify what your data will look like. For example, they might specify that a Person data instance has a name string field and an age integer field. If you come from Java or Cyou know what types are, but Haskell uses them very differently. In Haskell, types are used to express, encode, and enforce the requirements of your program as much as possible. The guideline is that invalid program states should not be expressible in the types you define.
At this point in the process, programming in Haskell is a typical data modeling exercise. We want to know what kind of entity is receiving the contribution. The following declaration states that a can be either a Candidatewhich must have year information and party information; a Committeewhich must have only a year; or a StateLevelwhich must have a year and a state code. Each row of the data file will have information about a single contribution made by an individual or organization.
FromField and FromNamedRecord are type classes.
In object-oriented terms, these are similar to small interfaces, some only declaring one or two methods. Data types can implement the type classes that make sense, but omit the ones that do not.