[Haskell-cafe] Re: [Haskell] Re: Global Variables and IO initializers

[Peter Simons]

Adrian Hey writes:

 > Perhaps you would like to show me your solution to the
 > "oneShot" problem.

I don't see any value in problems that are specifically
designed so that they can be solved only with a global
entity. What is the real-world application for oneShot?


 > If this is such a wacky idea then why is the use of the
 > unsafePerformIO hack to do precisely this so common place?

Because programmers tend to be lazy. I like Haskell because
it doesn't _allow_ me to be lazy.


 > I gather it's even used within ghc. If the two Simons
 > don't know how to write "proper" Haskell, what hope is
 > there for the rest of us.

Nobody said that. Use of unsafePerformIO does not equal bad
code.


 > But why would it be a problem if it was not?

Because code like that is very hard to get right and very
hard to maintain, and I don't want to use library code that
uses this technique if I can avoid it.

I'll be readily convinced of the opposite once I see code
that makes good use of this.

Peter