Notes (OFVB 07/31): When Things Go Wrong


Reworked take and drop to use pattern matching rather than nested ifs.



Trying and catching here seems not as good as just using a fold with a 0 default.


In my opinion, pure code is easier to reason about than impure code. Exceptions are inherently impure, and therefore are much better suited to IO than to e.g. the math examples in this chapter. In such cases, it is better to restrict the domain of function inputs, than extend the range of function outputs. A Natural number type is a better solution to the sqrt_floor problem, than a NegativeArgument exception. The former reduces the complexity of our code, the latter adds to it. Sometimes the only way to solve a problem is by adding complexity, but as a genral rule of thumb, the lowest complexity approach is usually best.