4 ms·

As someone who is interesting in writing more Haskell, I've heard all the "if I get it to compile it works perfectly the first time", and I wonder if people are

by dkubb 14y ago

As someone who is interesting in writing more Haskell, I've heard all the "if I get it to compile it works perfectly the first time", and I wonder if people are missing out on what proper TDD can bring them. At first TDD becomes a way to assert your code does what you expect. After a few years you begin to use it as a design technique, and the correctness argument becomes less and less of a reason for using it. It's more of an (albeit nice) side effect at that point. I can write code that I test after the fact and still get the same correctness benefits, but the feedback I get from testing my design is gone. Maybe I'm missing something, but I don't know if just having an excellent type checker is enough to provide the same quality feedback loop as well executed TDD does.

tikhonj 14y ago
You can use the types the same way--define your types and write type signatures for your functions before implementing them. I've found this particularly useful when writing really confusing code (like a Prolog interpreter, for example). Coming up with the types on a function clarifies what it has to do and shrinks the space of possible solutions significantly. Types are a symbolic way to reason about code. Using types, you can get additional insight into how your function can be written just by following some simple rules. A good example of this is realizing that a function you're working on is actually a specific version of a more general function--you can see this if the type signatures look similar. This lets you reuse very high-level, generic code easily. Going back to the Prolog example, I was having some trouble figuring out how the resolution algorithm should work. Then I realized that the sub-part I was having problems with was just special type of fold. This helped me get a very concise version of the function by reusing an existing library function. So types can provide exactly the same sort of benefits as TDD.

by dkubb 14y ago

tikhonj 14y ago

You can use the types the same way--define your types and write type signatures for your functions before implementing them. I've found this particularly useful when writing really confusing code (like a Prolog interpreter, for example). Coming up with the types on a function clarifies what it has to do and shrinks the space of possible solutions significantly. Types are a symbolic way to reason about code. Using types, you can get additional insight into how your function can be written just by following some simple rules. A good example of this is realizing that a function you're working on is actually a specific version of a more general function--you can see this if the type signatures look similar. This lets you reuse very high-level, generic code easily. Going back to the Prolog example, I was having some trouble figuring out how the resolution algorithm should work. Then I realized that the sub-part I was having problems with was just special type of fold. This helped me get a very concise version of the function by reusing an existing library function. So types can provide exactly the same sort of benefits as TDD.