Rafael Cunha de Almeida wrote:
I don't think that safeSecondElement is worse than secondElement. I think it's
better for the program to crash right away when you try to do something that
doesn't make sense.
Getting the secondElement of a list with one or less elements doesn't make
sense, so you
Gregory Crosswhite wrote:
Yes, but I think that it is also important to distinguish between cases
where an error is expected to be able to occur at runtime, and cases
where an error could only occur at runtime *if the programmer screwed up*.
Well sure, but how can you demonstrate that you (the
On May 9, 2010, at 1:04 AM, wren ng thornton wrote:
If you're structuring your code with that invariant, then why aren't you
using the correct type?
I do try to use the type system as much as possible to enforce constraints.
However. it is not always so simple as making sure that a list
On May 3, 2010, at 12:14 , Henning Thielemann wrote:
Ketil Malde schrieb:
Henning Thielemann lemm...@henning-thielemann.de writes:
http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow
I see. This should be forbidden, at all! :-)
Why is this
On May 4, 2010, at 12:31 , Gregory Crosswhite wrote:
On May 4, 2010, at 5:22 AM, John Lato wrote:
Crashing at the point of the error isn't necessarily useful in
Haskell due to lazy evaluation. The code will crash when the result
of the partial function is evaluated, which may be quite far away
* On Sunday, May 02 2010, Alexander Dunlap wrote:
Of course, there are situations where it is really awkward to not use
partial functions, basically because you *know* that an invariant is
satisfied and there is no sane course of action if it isn't. To take a
contrived example:
f ys = let xs =
From: Rafael Cunha de Almeida assina...@kontesti.me
Ivan Miljenovic ivan.miljeno...@gmail.com disse:
On 3 May 2010 14:17, aditya siram aditya.si...@gmail.com wrote:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function
On Tue, May 4, 2010 at 9:09 AM, Limestraël limestr...@gmail.com wrote:
Are there other methods than Maybe or exceptions to handle the errors in
Haskell? Is the monad Error(T) useful?
I believe the usual Error monad is just (Either e), with Left
indicating failure. It's the same idea as Maybe,
On Tue, May 4, 2010 at 2:09 PM, Limestraël limestr...@gmail.com wrote:
2010/5/4 John Lato jwl...@gmail.com
Crashing at the point of the error isn't necessarily useful in
Haskell due to lazy evaluation. The code will crash when the result
of the partial function is evaluated, which may be
On Tue, May 4, 2010 at 5:31 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:
Yes, but I think that it is also important to distinguish between cases where
an error is expected to be able to occur at runtime, and cases where an error
could only occur at runtime *if the programmer
This whole thing seems to be touching on something I saw recently and was
quite interested in. I found a site talking about static contract checking
in Haskell, unfortunately I can't seem to find it now, but this paper (
I definitely like that idea. :-) Is this similar to the notion of dependent
types?
Cheers,
Greg
On May 4, 2010, at 11:21 AM, Kyle Murphy wrote:
This whole thing seems to be touching on something I saw recently and was
quite interested in. I found a site talking about static contract
On Tue, May 4, 2010 at 2:43 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:
I definitely like that idea. :-) Is this similar to the notion of
dependent types?
That's where things tend to wind up eventually, yes. Although, with
Haskell as it stands, a great deal of unused information
The papers are available here: http://gallium.inria.fr/~naxu/pub.html
But in general you can say things like the following:
(Dana Xu uses a slightly different notation that I can never remember).
sorted :: Ord a = [a] - Bool
sorted [] = True
sorted [x] = True
sorted (x:xs) = x head xs
This is awesome! GHC-devs , please mainline the CONTRACT pragma.
-deech
On 5/4/10, Edward Kmett ekm...@gmail.com wrote:
The papers are available here: http://gallium.inria.fr/~naxu/pub.html
But in general you can say things like the following:
(Dana Xu uses a slightly different notation that
aditya == aditya siram aditya.si...@gmail.com writes:
aditya This is awesome! GHC-devs , please mainline the CONTRACT
aditya pragma.
I think it needs a LOT more work before it is usable. (I hope I'm wrong,
but Dana reckoned it needed about 7 more man-years of work.)
Dana sent me a
G'day all.
Quoting aditya siram aditya.si...@gmail.com:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a function and is the same as:
f x s = ...
Off the top of my head the State monad makes
On 03/05/2010, at 06:02, Jaco van Iterson wrote:
I was just wondering what methods are best to design/model the software in
bigger projects when you are planning to use Haskell.
Is there no difference compared to other languages? Are there any Haskell
tools?
In addition to what Don said,
Ivan Miljenovic ivan.miljeno...@gmail.com disse:
On 3 May 2010 14:17, aditya siram aditya.si...@gmail.com wrote:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a function and is the same as:
f x s =
Don Stewart d...@galois.com writes:
Some key points:
* Avoid partial functions
As an important corollary to this one I would add: never throw
exceptions from pure code. They often leak out from catch blocks and
ruin your day.
G
--
Gregory Collins g...@gregorycollins.net
On Mon, 3 May 2010, Gregory Collins wrote:
Don Stewart d...@galois.com writes:
Some key points:
* Avoid partial functions
As an important corollary to this one I would add: never throw
exceptions from pure code. They often leak out from catch blocks and
ruin your day.
It's not
Henning Thielemann lemm...@henning-thielemann.de writes:
It's not possible to throw exceptions from pure code. You can only
call 'error' and that's another name for 'undefined', i.e. you have a
partial (non-total ?) function.
Henning Thielemann lemm...@henning-thielemann.de writes:
http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow
I see. This should be forbidden, at all! :-)
Why is this worse than or different from 'error'? To me it looks like
'error', only with a
Ketil Malde schrieb:
Henning Thielemann lemm...@henning-thielemann.de writes:
http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow
I see. This should be forbidden, at all! :-)
Why is this worse than or different from 'error'? To me it looks
Ketil Malde ke...@malde.org writes:
Henning Thielemann lemm...@henning-thielemann.de writes:
http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow
I see. This should be forbidden, at all! :-)
Why is this worse than or different from 'error'?
Gregory Collins g...@gregorycollins.net writes:
Henning Thielemann lemm...@henning-thielemann.de writes:
http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow
I see. This should be forbidden, at all! :-)
Why is this worse than or different from
Hi
I was just wondering what methods are best to design/model the software in
bigger projects when you are planning to use Haskell.
Is there no difference compared to other languages? Are there any Haskell
tools?
Cheers,
Jaco
PS.
Software design in Haskell didn't give relevant hits. :(
jaco.van.iterson:
Hi
I was just wondering what methods are best to design/model the software in
bigger projects when you are planning to use Haskell.
Is there no difference compared to other languages? Are there any Haskell
tools?
I don't believe anyone has written a Programming Haskell
On Sun, May 2, 2010 at 4:10 PM, Don Stewart d...@galois.com wrote:
I don't believe anyone has written a Programming Haskell in the Large
book (or any other similar functional language??), but there is lots of
experience in this community working on big, long lived code bases.
Some key points:
brad.larsen:
On Sun, May 2, 2010 at 4:10 PM, Don Stewart d...@galois.com wrote:
I don't believe anyone has written a Programming Haskell in the Large
book (or any other similar functional language??), but there is lots of
experience in this community working on big, long lived code bases.
On Sun, 02/May/2010 at 13:10 -0700, Don Stewart wrote:
* Avoid partial functions
Why?
Edgar
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
On 3 May 2010, at 02:18, Edgar Z. Alvarenga wrote:
On Sun, 02/May/2010 at 13:10 -0700, Don Stewart wrote:
* Avoid partial functions
Why?
Tell you tomorrow.
Conor
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
On 3 May 2010 11:18, Edgar Z. Alvarenga ed...@ymonad.com wrote:
On Sun, 02/May/2010 at 13:10 -0700, Don Stewart wrote:
* Avoid partial functions
Why?
What does head [] do again?
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
On Sun, May 2, 2010 at 9:18 PM, Edgar Z. Alvarenga ed...@ymonad.com wrote:
On Sun, 02/May/2010 at 13:10 -0700, Don Stewart wrote:
* Avoid partial functions
Why?
Edgar
Ever place you use a partial function, you need to verify that its
usage is in fact safe. Otherwise, you risk pattern
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a function and is the same as:
f x s = ...
Off the top of my head the State monad makes extensive use if this
style. Is this bad?
- deech
On 5/2/10,
On 3 May 2010 14:17, aditya siram aditya.si...@gmail.com wrote:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a function and is the same as:
f x s = ...
No, that's a partially applied function.
A
Cool. That makes way more sense.
I thought that ghc -Wall picked these up. So at least this problem
would go away if warnings were turned on (and heeded) by default.
Besides that from my own experience I'd strongly encourage people to
use HLint [1] .
-deech
[1 ]
On Sun, May 2, 2010 at 9:24 PM, Ivan Miljenovic
ivan.miljeno...@gmail.com wrote:
On 3 May 2010 14:17, aditya siram aditya.si...@gmail.com wrote:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a
On 3 May 2010 14:35, Alexander Dunlap alexander.dun...@gmail.com wrote:
Of course, there are situations where it is really awkward to not use
partial functions, basically because you *know* that an invariant is
satisfied and there is no sane course of action if it isn't.
True, like map head .
On May 3, 2010, at 6:35 AM, Alexander Dunlap wrote:
Of course, there are situations where it is really awkward to not use
partial functions, basically because you *know* that an invariant is
satisfied
That falls under Don's: Use types to encode the design into a machine
checkable form
Or
40 matches
Mail list logo
