Unit Testing – Why No Parameters Are Better Than Few Parameter Methods

I don’t use F#, but in Haskell it is considered good form to annotate (at least) top-level definitions, and sometimes local definitions, even though the language has pervasive type inference. This is for a few reasons:

• Reading
  When you want to know how to use a function, it’s incredibly useful to have the type signature available. You can simply read it, rather than trying to infer it yourself or relying on tools to do it for you.

• Refactoring
  When you want to alter a function, having an explicit signature gives you some assurance that your transformations preserve the intent of the original code. In a type-inferred language, you may find that highly polymorphic code will typecheck but not do what you intended. The type signature is a “barrier” that concretises type information at an interface.

• Performance
  In Haskell, the inferred type of a function may be overloaded (by way of typeclasses), which may imply a runtime dispatch. For numeric types, the default type is an arbitrary-precision integer. If you don’t need the full generality of these features, then you can improve performance by specialising the function to the specific type you need.

For local definitions, let-bound variables, and formal parameters to lambdas, I find that type signatures usually cost more in code than the value they would add. So in code review, I would suggest you insist on signatures for top-level definitions and merely ask for judicious annotations elsewhere.

The main reason is for performance. The "unlimited arguments" syntactical sugar is actually an array of Strings. If you are only passing one string, why create an array with only one string? Especially if ~90% of the invocations of this method will be with 3 or fewer arguments, there is no need for the heavier weight array object. It's a little lighter in memory and takes a little less processing time because you don't need a loop in order to define the method. If you have three strings, you just code for three strings.