[Haskell-cafe] Re: [Haskell] Top Level <-

Lennart Augustsson lennart at augustsson.net
Wed Aug 27 19:15:10 EDT 2008

I didn't say NetBSD doesn't use global variables, I said the device
driver model doesn't use global variables.
And quite a few things that used to be in global variables have been
moved into allocated variables and are being passed around instead.
That's simply a better way to structure the code.

I don't don't think global variables should be banned, I just think
they should be severly discouraged.

On Wed, Aug 27, 2008 at 11:25 PM, John Meacham <john at repetae.net> wrote:
> On Wed, Aug 27, 2008 at 12:17:46PM -0500, Derek Elkins wrote:
>> On Wed, 2008-08-27 at 02:35 -0700, John Meacham wrote:
>> > However, note the weasel words. Those are in there on purpose, every
>> > design calls for different solutions. To blanketly say certain
>> > constructs are just wrong to the point of disallowing them in the
>> > language, especially when they are common practice at the moment, just
>> > doesn't seem right.
>> How can a Haskell user say this?  And this is indeed exactly what
>> capability languages do.  In fact, this is what almost every language
>> does (for one thing in common practice or another.)
> But as a system designer I *need* things like peek/poke/ACIO etc. I am
> the one implementing 'Random' or 'Data.Unique'. If I have to resort to C
> code to do such things, that makes haskell unsuitable for a wide variety
> of systems programming tasks (including implementing the haskell 98
> libraries). I know it is certainly possible to do a lot of things in a
> capability-based system. but you don't always want or have the ability
> to use such a system.
> I am not sure why it was thought netbsd didn't use global state. a
> simple grep of the kernel headers for '^extern' turns up hundreds of
> them. even pure capability based systems such as EROS need it for their
> implementation. What such systems strive for is no or reduced state in
> their interface. which is a very different thing and also something that
> I strive for in haskell code. (and is fairly easy to achieve actually)
>        John
> --
> John Meacham - ⑆repetae.net⑆john⑈
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