[Haskell-cafe] newbe question
Hi i can not load program test1 into hugs, but test2 works. Am i missing some special syntax? greetings, Philip -- test1 -- foo :: Maybe Int - Int foo Nothing =-1 foo (Just a)= a -- test2 -- foo :: Maybe Int - Int foo Nothing = -1 -- ^ -- +-- note an extra space foo (Just a)= a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
The reason is that you can define =- as on operator so for example, in this (obfuscated) code: (=-) x y = x * y sq y = y =- y Thus, in your code, you had an operator on the LHS of the definition, and the interpreter baulked at it. Bob On 27 Sep 2005, at 10:34, [EMAIL PROTECTED] wrote: Hi i can not load program test1 into hugs, but test2 works. Am i missing some special syntax? greetings, Philip -- test1 -- foo :: Maybe Int - Int foo Nothing =-1 foo (Just a)= a -- test2 -- foo :: Maybe Int - Int foo Nothing = -1 -- ^ -- +-- note an extra space foo (Just a)= a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
Am Dienstag, 27. September 2005 11:34 schrieb [EMAIL PROTECTED]: Hi i can not load program test1 into hugs, but test2 works. Am i missing some special syntax? greetings, Philip -- test1 -- foo :: Maybe Int - Int foo Nothing =-1 foo (Just a)= a -- test2 -- foo :: Maybe Int - Int foo Nothing = -1 -- ^ -- +-- note an extra space foo (Just a)= a Hello, obviously, Hugs thinks that =- is a special operator. In Haskell you have the ability to define your own operators, so it would be possible to define an operator =-. I would suggest that you always put spaces around the = in declarations. Best wishes, Wolfgang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
On 27 Sep, Wolfgang Jeltsch wrote: Hello, obviously, Hugs thinks that =- is a special operator. In Haskell you have the ability to define your own operators, so it would be possible to define an operator =-. I would suggest that you always put spaces around the = in declarations. Best wishes, Wolfgang Hello, thank you for fast reply. Ok, but what is the semantic of '=-' ? If it's an operator, it should have some impact (right term?). Greetings, Philip ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
On 27 Sep 2005, at 16:53, [EMAIL PROTECTED] wrote: On 27 Sep, Wolfgang Jeltsch wrote: Hello, obviously, Hugs thinks that =- is a special operator. In Haskell you have the ability to define your own operators, so it would be possible to define an operator =-. I would suggest that you always put spaces around the = in declarations. Best wishes, Wolfgang Hello, thank you for fast reply. Ok, but what is the semantic of '=-' ? If it's an operator, it should have some impact (right term?). The semantics are whatever you define them to be: (=-) x y = doSomeFunkyStuff x y Note that this also introduces problems with comments, a common mistake people make is to not put a space after the -- comment symbol, so they may end up with: --| something The compiler then interprets --| as an operator. Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Help wanted: Lazy multiway zipper with mismached intervals
Many thanks to all for the replies From: ChrisK [EMAIL PROTECTED] Could the interval for element x of List xList overlap with more than one element of another list? It does not matter too much, but is something you did not clarify. In general, how may the intervals for all the lists overlap? (The answer may be too complex, in which case you can just ignore me). Yes, unlimited overlap is possible. e.g. Infinite interval in one list, and infinitely many small intervals in another list. I would start by merging, perhaps in stages, into an intermediate list with elements of its own data FooIntermediate = A _ [_]| B _ [(_,_)] | C _ _ _ | ... types. Yes, I'll probably use this suggestion, maybe with records to make partial update easier. If you need to change the semantics of merging the streams then it may help when you refactor that the types of events are now types of constructors and the compiler is checking your code. Originally I had thought that I could treat the merge symetrically, but I now think this is not the case. Still I am not sure if I will use different types for different types of merge. Rene. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Neural networks and optimization in Haskell
Folks, I got a project where I have a large number of variables and an outcome and I need to figure out which 20% of the variables has the largest effect on the outcome. Of course I also need to optimize the 20% of variables I end up with. This sounds like a job for a neural network to me, with arguments possibly optimized through genetic algorithms. I'm wondering, though, if I'm complicating things for myself and there's an easier approach to this. If not I'm wondering if there are ready-made NN or GA libraries for Haskell. Also, I'm curious if Haskell is really the best language for this type of problem and if lazy evaluation brings any specific advantages to the solution or would be a hindrance. I would welcome any pointers and feedback, yes, someone is actually paying me to do this :-). Thanks, Joel -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] XMLParse module
Hello all, I am reading XMLParse module http://www.germane-software.com/repositories/public/StatusReport/trunk/hxml-0.2/XMLParse.hs But, I am not clear about the purpose of this module and the function of two functions: parseInstance = unfoldr (pRun instanceItem) . pcdataModeparseDTD = foldl (\a b-b a) emptyDTD . unfoldr (pRun dtdItem) . markupModeparseDocument text = case pRun prolog (pcdataMode text) of Just (_, rest) - unfoldr (pRun instanceItem) rest Nothing - [ErrorEvent Error parsing prolog] -- can't happen. If any knows the meaning of those, please let me know. Thanks a lot. Best regards, ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
[EMAIL PROTECTED] wrote: obviously, Hugs thinks that =- is a special operator. In Haskell you have the ability to define your own operators, so it would be possible to define an operator =-. I would suggest that you always put spaces around the = in declarations. Best wishes, Wolfgang Hello, thank you for fast reply. Ok, but what is the semantic of '=-' ? If it's an operator, it should have some impact (right term?). It isn't defined in the prelude or any of the standard libraries. The point is that the Haskell tokeniser treats any consecutive sequence of the symbols !#$%*+./=[EMAIL PROTECTED]|-~ as a single operator token. This occurs regardless of whether a definition exists for the operator. More generally, the tokenising phase is unaffected by whether or not an operator, constructor, identifier etc is defined. A specific sequence of characters will always produce the same sequence of tokens regardless of what definitions exist. -- Glynn Clements [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] newbe question
On 27 Sep, Glynn Clements wrote: It isn't defined in the prelude or any of the standard libraries. The point is that the Haskell tokeniser treats any consecutive sequence of the symbols !#$%*+./=[EMAIL PROTECTED]|-~ as a single operator token. This occurs regardless of whether a definition exists for the operator. More generally, the tokenising phase is unaffected by whether or not an operator, constructor, identifier etc is defined. A specific sequence of characters will always produce the same sequence of tokens regardless of what definitions exist. Thank you, that is the problem i am wrestling with. -Philip ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
