The Pragmatic Programmer - How to use Exceptions

Coincidence Risks

Programming by coincidence can lead to unreliable and unpredictable code, as Alan Underwood and Michael Outlaw discuss. They emphasize the importance of avoiding assumptions and ensuring code is well-documented and adheres to a clear contract. Alan warns against the dangers of making changes without understanding the underlying code, as it can introduce performance issues and regressions 1. Underwood shares his own experience, admitting,

I was actually really irritated with myself because the code was doing the wrong thing, but it was working. Doing the wrong thing for a long time. And this is what programming by coincidence is, right?

--- Alan Underwood

He emphasizes the importance of avoiding implicit assumptions and ensuring that code is well-documented and reliable 1.

   

Exception Strategy

The discussion then shifts to the strategic use of exceptions in programming. Michael Outlaw and Alan Underwood explore when it's appropriate to throw exceptions, emphasizing that they should be reserved for truly unexpected events. They caution against relying on implicit exception throwing, such as assuming a file exists without checking, which can lead to unintended errors and performance issues 1. Underwood emphasizes the importance of verifying assumptions, stating:

Don't assume something, prove it. Assumptions that aren't based on fact become a major sticking point in many cases.

--- Alan Underwood

The hosts encourage developers to avoid programming by coincidence and to ensure their code is both understandable and reliable 1 1.