Re: Proposal: System.Environment.getEnv should return Maybe

On Wed, Feb 22, 2012 at 3:51 PM, John Meacham wrote:

On Wed, Feb 22, 2012 at 3:05 PM, Evan Laforge wrote:

...

It's awkward and surprising how getEnv throws an exception when an env var is not set, since it's very common for env vars to be optional, and it's not convenient to catch exceptions in haskell (I have to look up Control.Exception every time, and then add LANGUAGE

For true IO exceptions, you should be using the Prelude.catch mechanism. It's the right thing to do and makes your program more portable as a bonus. It is quite unfortunate that IO exceptions became conflated with imprecise and dynamic exceptions and clash in their names. They really are different beasts alltogether.

Good point, I had forgotten about the Prelude catch. I think I can go remove a bunch of ScopedTypedVariables now. The ghc exception situation is a bit messy, and I never have all the distinctions quite memorized, but it's also because I hardly ever have to deal with exceptions (of the "magical return value" variety, I use Either and Maybe all the time), unlike certain other languages. And that's a very good thing! If I forget the rest about exceptions due to lack of use, I should at least remember that IO exceptions are different from, and better behaved than, the imprecise ones.