Re: Debugging haskell
Dave Tweed wrote: If you discard `compliation preventing, very very quick to solve' bugs (e.g., missing semi-colons in C++, silly typecheck errors in Haskell) I find that the ratio between source code bugs and algorithm bugs is maybe 1:5. This means that whilst I find Haskell a great deal easier to write correctly than C++, there's not that much difference between debugging times for Haskell and C++ because the algorithm level bugs dominate. In my experience, the number of algorithm bugs is usually about the same, regardless of which language you're using. And simple source code bugs are no real problem in any language. But because there's more translation involved in rendering a mental model of an algorithm in C++ than in Haskell, there's much more opportunity for introducing more subtle source code bugs. I find that I very rarely have these kinds of bugs in Haskell (and the type-checker usually catches them anyway), but they were always the largest proportion of bugs when I used to program in C, etc. A -- Andy Moran Ph. (503) 526 3472 Galois Connections Inc. Fax. (503) 350 0833 3875 SW Hall Blvd.http://www.galois.com Beaverton, OR 97005[EMAIL PROTECTED] ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [off-topic] LaTex for [[ ... ]]
Joe English wrote:
Fergus Henderson wrote:
Sorry for the off-topic post, but I figured someone here would know...
can anyone please tell me how to do the double-square-bracket symbols
that are often used in denotational semantics in LaTex? It's like
[[ but a single symbol without the space between the two brackets.
It's often done by squishing together two ordinary square brackets
with a negative thin space (\!):
\newcommand{\sembrack}[1]{[\![#1]\!}
This looks good with Computer Modern; with other fonts YMMV.
There's also \llbracket and \rrbracket, from stmaryrd. They look better than
the negative space hack, IMHO (now all I need is for Alan Jeffrey to write in
and say that \{ll,rr}bracket are implemented with the negative space hack :-)
Cheers,
Andy
--
Andy Moran Ph. (503) 526 3472
Galois Connections, Inc.Fax. (503) 350 0833
3875 SW Hall Blvd. http://www.galconn.com
Beaverton, OR 97005 [EMAIL PROTECTED]
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Re: GHCi command line
Julian Seward (Intl Vendor) wrote: It's a known issue^H^H^H^H^Hbug. I don't think we yet have a story about how to fix this. How about a :main args which sets the appropriate environment variables to args? Or would that affect GHCi's settings? Cheers, Andy -- Andy Moran Ph. (503) 526 3472 Galois Connections, Inc.Fax. (503) 350 0833 3875 SW Hall Blvd. http://www.galconn.com Beaverton, OR 97005 [EMAIL PROTECTED] ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
GHCi command line
Running a main that calls getArgs inside GHCi yields the arguments to GHCi, not main. Any way around this? Cheers, Andy -- Andy Moran PacSoft x7557 Computer Science Engineering+1 503 748 7557 Oregon Graduate Institute http://www.cse.ogi.edu/~moran ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: types with value parameter (another example of application)
[EMAIL PROTECTED] writes: Andrew J. Kennedy. Dimension Types. In ESOP '94: Proceedings of the Fifth European Symposium on Programming, Lecture Notes in Computer Science 788. Springer-Verlag, 1994 Available electronically from the out-of-date home page http://www.cl.cam.ac.uk/~ajk13/ Mikael Rittri followed up this work: Mikael Rittri. Dimension inference under polymorphic recursion. In FPCA'95: Proceedings of the 7th ACM Conf. on Functional Programming Languages and Computer Architecture, La Jolla, California. Pages 147-159. ACM Press 1995. http://ftp.cs.chalmers.se/users/pub/rittri/dimpolyrec.ps.Z He adds polymorphic recursion (for dimensions) to Kennedy's type system. This allows, e.g., definition of a datatype for polynomials that has the correct dimension type and functions over it (the latter requires the polymorphic recursion). Cheers, Andy
Re: Haskell 2 -- Dependent types?
Lennart Augustsson writes: OK, I'm curious. Two people replied that C++ has undecidable type checking. I was not aware of this (although I can't say I'm too surprised); do you have a reference? It's actually the template processing that can loop, but it is sort of part of the type checking. You can find an article in the POPL 99 proceeding about it. Actually, I think Lennart means PEPM '99. At least, there's an article called "C++ Templates as Partial Evaluation" by Todd Veldhuizen (from the wonderfully-named Extreme Computing Laboratory) which refers to this. He cites an example of using the templates to generate a list of prime numbers at compile time due to Erwin Unruh (apparently discovered accidentally!). Cheers, Andy
Re: Formal design spec into Haskell or Miranda
Andrew Butterfield writes: At 15:41 +0100 20/10/97, Greg Michaelson wrote: (rearranged by me for dramatic effect :-) But you should look at the Jones and Hayes paper from Software Engineering Journal called something like "Executions are not (always) executable" I think Greg means "_Specifications_ are not (necessarily) executable", by Ian Hayes and Cliff Jones. It appeared in the Software Engineering Journal, 4(6):330--338, November 1989. Cheers, Andy
Re: A new view of guards
Brian Boutel writes: The - syntax worries me a bit, because in the comprehension use it has a different type, but the let syntax is available, and one can write "let p = e" "for p - e". I think that, to reduce possible confusion, I would use, and teach, the let form. Given that, I don't object to the funny use of -. Good point, but now one has too many ='s: simplify (Plus e e') | let (Val 0) = s = s' | let (Val 0) = s' = s | otherwise= Plus s s' where s = simplify e s' = simplify e' I think that's very confusing too. Cheers, Andy
