[Haskell] pros and cons of static typing and side effects ?

Simon Peyton-Jones simonpj at microsoft.com
Fri Aug 12 03:28:19 EDT 2005

Perhaps this discussion could move to Haskell-café?  We try to keep the bandwidth on Haskell at haskell.org fairly low.


| -----Original Message-----
| From: haskell-bounces at haskell.org [mailto:haskell-bounces at haskell.org] On Behalf Of John Meacham
| Sent: 12 August 2005 00:47
| To: haskell at haskell.org
| Subject: Re: [Haskell] pros and cons of static typing and side effects ?
| On Thu, Aug 11, 2005 at 03:40:25PM -0400, Hamilton Richards wrote:
| > At 10:40 PM +0200 2005/8/10, mt wrote:
| > >... Languages with
| > >static typing would be more suitable if programs were something you thought
| > >of in advance, and then merely translated into code. But that's not how
| > >programs get written.
| >
| > Well, that is actually how lots of programs do get written.
| >
| > For software that is experimental and exploratory, whose code
| > undergoes continual change and whose only users are the code's
| > authors, static typing is arguably a dispensable nuisance. A type
| > error that pops up during execution is probably no more inconvenient
| > than one that's caught by static type checking. That's why Lisp is
| > popular for AI work.
| I find pretty much completly the opposite is true. for random hacking
| and evolving code, static typing is essential. There is only so much
| room in one's brain to keep track of how everything works. if you were
| meerly translating from a previous design, this isn't so much an issue.
| but when writing code that is evolving and changing and perhaps you
| don't quite know how it will turn out, your ability to recall and
| understand how everything works together is a major limiting factor on
| the scope of what you can acomplish. Static typing offloads a _ton_ of
| responsibility away from the programmer. you no longer need to worry or
| even think about what types are held in variables because you know any
| mistakes will be caught by the compiler. and with haskell's advanced
| type system, you can encode much more advanced constraints and
| invarients in the type system offloading even more work from your brain.
| Haskell's strong type system made me writing jhc alone possible, not
| because of the better reliability (that is great though!), but because
| it let me 'forget' about so many inconsequential details that they type
| system enforced so I only needed to use brain-space for high level
| constructs and my overall evolving, changing, plan. I tend to only use
| perl or other dynamically typed languages when writing something that I
| know exactly what it will do and how to do it beforehand, because I find
| it to be quite an inflexible language when it comes to changing code
| after the fact, not because of any syntatic difficulty, but because you
| basically have to constantly redervive everything the program does and
| all the unspoken invarients to understand it and how to change it. which
| is something that gets super-linearly harder as code size grows.
|         John
| --
| John Meacham - ⑆repetae.net⑆john⑈
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