Re: Haskell conventions (was: RE: how to write a simple cat)

On Fri, 11 Jun 1999, Erik Meijer wrote: > > Personally I find the convention of using `a', `b', and `c' for type > > variables to be a poor one. I much prefer using `t' (if there's > > only one) or `t1', `t2', ... (if there's more than one). > > I find that for me this makes it much easi

Re: Haskell conventions (was: RE: how to write a simple cat)

Jan Skibinski wrote: > > On Fri, 11 Jun 1999, Craig Dickson wrote: > > > I don't see that underscores serve readability in the same way as Hungarian > > notation purports to (unless the Eiffel people claim that underscores > > somehow convey type information?), so I don't see a conflict here. On

Re: Haskell conventions (was: RE: how to write a simple cat)

> So, the name of a type is always at least a full word, as are the names of > specific functions. But type variables are almost always single > characters, and distinct from the names of any type. Conventionally, they > are also usually "a", "b", and "c", although "m" is for monad. Personally

Re: Haskell conventions (was: RE: how to write a simple cat)

> Personally I find the convention of using `a', `b', and `c' for type > variables to be a poor one. I much prefer using `t' (if there's > only one) or `t1', `t2', ... (if there's more than one). > I find that for me this makes it much easier to read type declarations, > because names like `a', `

Re: Haskell conventions (was: RE: how to write a simple cat)

> So, the name of a type is always at least a full word, as are the names of > specific functions. But type variables are almost always single > characters, and distinct from the names of any type. Conventionally, they > are also usually "a", "b", and "c", although "m" is for monad. > Convention

Re: how to write a simple cat

> >I disagree, small scripts spend most of the time doing I/O if I don't > >understand how to do that I'm not able to even write the most simple > >things. This is eg. true for my cat ... > > I disagree. You need to know more about Functional Programming > (and also the Haskell type system and it

Re: Haskell conventions (was: RE: how to write a simple cat)

Jonathan King writes: > So, the name of a type is always at least a full word, as are the names of > specific functions. But type variables are almost always single > characters, and distinct from the names of any type. Conventionally, they > are also usually "a", "b", and "c", although "m" is

RE: Haskell conventions (was: RE: how to write a simple cat)

Jonathan King wrote: > > transformListElems :: (elem -> elem') -> List elem -> List elem' > > transformListElems transform Nil = Nil > > transformListElems transform (Cons elem elemRest) = > > Cons (transform elem) (transformListElems transform elemRest) > > Well, the second version does

Re: Haskell conventions (was: RE: how to write a simple cat)

On Fri, 11 Jun 1999, Craig Dickson wrote: > I don't see that underscores serve readability in the same way as Hungarian > notation purports to (unless the Eiffel people claim that underscores > somehow convey type information?), so I don't see a conflict here. One could > easily use both, e.g.

Re: Haskell conventions (was: RE: how to write a simple cat)

Christian Sievers <[EMAIL PROTECTED]> wrote: > I'm in trouble when it comes to @-patterns: is xs@(x:_) acceptable? I'm sure I've used that, or something quite like it. xs is the whole list, and x is its head. > I've seen the (x:xs) (or whatever letter you want, BTW I'd use (f:fs) > for a list o

Re: Haskell conventions (was: RE: how to write a simple cat)

On Fri, 11 Jun 1999, Jan Skibinski wrote: > >Keith Wansbrough <[EMAIL PROTECTED]>, > > > > [[EMAIL PROTECTED] wrote stuff but got snipped] > > > > > > [stuff about whether there was a Haskell coding convention snipped] > > > > I think this kind of thing is valuable... Hungarian notation [1] >

Re: Haskell conventions (was: RE: how to write a simple cat)

> I think this kind of thing is valuable... Hungarian notation [1] > serves the same purpose in Windows C / C++ programming. It *is* > valuable having canonical variable names for most situations; it reduces the > intellectual load on the (human) reader of the code... you don't have to > chec

Re: Haskell conventions (was: RE: how to write a simple cat)

Jan Skibinski <[EMAIL PROTECTED]> wrote: > But there are some stylistic camps, such as Eiffel's, that > prefer names with underscores rather than Hungarian notation > - claiming exactly the same reason: better readability. :-) I don't see that underscores serve readability in the same way as Hun

Re: how to write a simple cat

On 09-Jun-1999, Friedrich Dominicus <[EMAIL PROTECTED]> wrote: > What's a HOF? HOF is an acronym for Higher-Order Function. -- Fergus Henderson <[EMAIL PROTECTED]> | "I have always known that the pursuit WWW: | of excellence is a lethal habit" PGP: finger [EMAI

RE: how to write a simple cat

> > > > What is difficult is that by using some predefined function, one can > > > > express very much in very small code. I believe Haskell is even more > > > > expressive than most OO languages with comparable libraries > > > > (perhaps except Smalltalk, as that has also a very compact syntax).

Haskell conventions (was: RE: how to write a simple cat)

Well, the cat has been skinned and boned, but I think I see a shread of meat or two that hasn't been picked over yet... On Thu, 10 Jun 1999, Frank A. Christoph wrote: [some attributions missing...I hope you know who you are] [big snip, about the fact that Haskell programs can be quite brief]

Re: how to write a simple cat

On Wed, 9 Jun 1999, Friedrich Dominicus wrote: [snip] > What's a HOF? > A Higher Order Function, the key to code reuse and abstraction. > > that first splits something up to a list using splitFn > > (or with the generalization I mentioned, to a monad), then maps a > > function over that list (na

RE: how to write a simple cat

To: [EMAIL PROTECTED] > Subject: Re: how to write a simple cat > > At 16:37 Uhr +0200 09.06.1999, Friedrich Dominicus wrote: > > > > I think exercise with the purely functional, non-I/O core (and perhaps > > > interact like someone else suggested) teaches you the m

Re: how to write a simple cat

At 16:37 Uhr +0200 09.06.1999, Friedrich Dominicus wrote: > > I think exercise with the purely functional, non-I/O core (and perhaps > > interact like someone else suggested) teaches you the mode of > > thinking in purely functional languages. That thinking can also > > help you understand the wa

Re: how to write a simple cat

Hannah Schroeter wrote: > > Hello! > > On Fri, Jun 04, 1999 at 12:18:31PM +0200, Friedrich Dominicus wrote: > > > [...] > > > > splitFilterMap unSplitFn afterMap filterPredicate beforeMap splitFn = > > > unSplitFn . map afterMap . filter filterPredicate . map beforeMap . splitFn > > [...] >

Re: how to write a simple cat

Hannah Schroeter wrote: > > Hello! > > On Fri, Jun 04, 1999 at 12:29:45PM +0200, Friedrich Dominicus wrote: > > [...] > > > > What is difficult is that by using some predefined function, one can > > > express very much in very small code. I believe Haskell is even more > > > expressive than mos

Re: how to write a simple cat

Hello! On Wed, Jun 02, 1999 at 01:29:12AM -0700, Simon Peyton-Jones wrote: > [...] > - Would people actually add stuff? I'm a bit skeptical, but it would >be great to have my skepticism proved unfounded. I think, Friedrich and those who helped him could have posted their questions and

Re: how to write a simple cat

Hello! On Fri, Jun 04, 1999 at 12:29:45PM +0200, Friedrich Dominicus wrote: > [...] > > What is difficult is that by using some predefined function, one can > > express very much in very small code. I believe Haskell is even more > > expressive than most OO languages with comparable libraries >

Re: how to write a simple cat

Hello! On Fri, Jun 04, 1999 at 12:18:31PM +0200, Friedrich Dominicus wrote: > [...] > > splitFilterMap unSplitFn afterMap filterPredicate beforeMap splitFn = > > unSplitFn . map afterMap . filter filterPredicate . map beforeMap . splitFn > [...] > sorry this looks morre terrible to me than a

Re: how to write a simple cat

Hans Aberg <[EMAIL PROTECTED]> writes: > Exactly how is this connection between the lambda calculus and > category theory described? -- That is, one would expect to know that > if one has a category of some sort, it is equivalent to the lambda > calculus, or something like that. There is a ver

Re: how to write a simple cat

Lennart Augustsson wrote: > > Friedrich Dominicus wrote: > > > That might be good advice but I/O is one of the most essential things > > and I have to know how to use it proper for writing small skripts. > > Actually, you can do a lot without learning about I/O. The function `interact' > > co

Re: how to write a simple cat

At 14:18 +0200 1999/06/04, Mariano Suarez-Alvarez wrote: >> >A ``category with + and ^ '' is called cartesian closed aditive >> >category, cf MacLane, Category Theory for the Working Mathematician >> >> Is this a suggestion or a theorem? > >A definition. I did not see the connection between the +

Re: how to write a simple cat

Friedrich Dominicus wrote: > That might be good advice but I/O is one of the most essential things > and I have to know how to use it proper for writing small skripts. Actually, you can do a lot without learning about I/O. The function `interact' converts a `String->String' function into an IO

Re: how to write a simple cat

On Thu, 3 Jun 1999, Hans Aberg wrote: > >A ``category with + and ^ '' is called cartesian closed aditive > >category, cf MacLane, Category Theory for the Working Mathematician > > Is this a suggestion or a theorem? A definition. -- m

Re: how to write a simple cat

> > So after I read in a chunk form that file > > into one large String, lines splits that line on a '\n' position. The > > lines li are filtered and l is one line a String-List which is added to > > fl all the filterd lines are then put back into on large String. Uff. Is > > that nearly correct?

Re: how to write a simple cat

> > Then split it up like you'd do in an OO language. I think, FP also > is good for writing small functions that do one thing well, and then > composing them in various ways (as you see, composing functions (and > perhaps also values) in Haskell is possible in very many various ways :-) ). > >

Re: how to write a simple cat

Hello! On Wed, Jun 02, 1999 at 08:12:04AM +0200, Friedrich Dominicus wrote: > [...] > this seems to to the thing I would like it to do. I now have to check if > the given fn is valid and raise an error if not so I do think I'll make > it;-) No you don't have to check fn. readFile checks and thr

Re: how to write a simple cat

At 20:08 +0200 1999/06/03, Mariano Suarez-Alvarez wrote: >A ``category with + and ^ '' is called cartesian closed aditive >category, cf MacLane, Category Theory for the Working Mathematician Is this a suggestion or a theorem? Hans Aberg * Email: Hans Aberg

Re: how to write a simple cat

On Wed, 2 Jun 1999, Hans Aberg wrote: > But it can be a spin-off for thoughts: A category is essentially an object > with I and *, and a functor is a map preserving those. So what about the > two other operations, + and ^ ?. A ``category with + and ^ '' is called cartesian closed aditive categor

Re: how to write a simple cat

Hello, Friedrich. On Tue, Jun 01, 1999 at 04:04:42PM +0200, Friedrich Dominicus wrote: > [...] > > longerThan :: String {- filename -} -> Int {- length limit -} -> IO () > > longerThan fn lenlim = do > > content <- readFile fn > > let li = lines content > > fl = filter (\l -> len

RE: how to write a simple cat

Simon Peyton-Jones writes: > Community-generated FAQ pages sound great, but > > - Some (standard? readily-available?) technology is needed to allow >people to add stuff without intervention from the site organiser. >The Wiki-Wiki-Web stuff indeed looks like a real possibility. I di

Re: how to write a simple cat

At 16:46 +0200 1999/06/02, Sven Panne wrote: >> [...] Then together with the identity I, +, * and ^ can be written >> out to be a primitive set for the lambda theory. That is, all lambda >> expressions can be generated from these symbols. > >Impressive! %-) Hmmm, I just thought about the possibl

Re: how to write a simple cat

Hans Aberg wrote: > But it can be a spin-off for thoughts: A category is essentially an object > with I and *, and a functor is a map preserving those. So what about the > two other operations, + and ^ ?. I somehow managed to delete Hans's earlier post in which he gives the definitions for + an

Re: how to write a simple cat

Hans Aberg wrote: > [...] Then together with the identity I, +, * and ^ can be written > out to be a primitive set for the lambda theory. That is, all lambda > expressions can be generated from these symbols. Impressive! %-) Hmmm, I just thought about the possible directions of this discussion

RE: how to write a simple cat

At 12:44 +0100 1999/06/02, Peter Hancock wrote: >> One reason flip(.) might be given a symbol similar to multiplication and >> flip($) a symbol similar to exponentiation is that on the Church integer >> functionals, these two operations are just the multiplication and >> exponentia

RE: how to write a simple cat

> "Hans" == Hans Aberg <[EMAIL PROTECTED]> writes: > One reason flip(.) might be given a symbol similar to multiplication and > flip($) a symbol similar to exponentiation is that on the Church integer > functionals, these two operations are just the multiplication and > expone

RE: how to write a simple cat

At 11:57 +0900 1999/06/02, Frank A. Christoph wrote: >> I just wish a standard operator is chosen for a) flip (.) and b) flip >> ($) instead of having everyone make up their own. I don't really care >> what it is. I truthfully like >.> for flip (.) and # for flip ($) but I >> can easily change.

RE: how to write a simple cat

> > > Do you want to drive me away from learning Haskell? Who the > hell can try > > > to write such functions? Is readabilty not a concern in Haskell? > > > > I would have to agree, Sven does seem to be working hard to drive a > > beginner away from Haskell. But he is illustrating an important >

RE: how to write a simple cat

> haskell.org is the obvious place. I'm sure John Peterson would be happy > to add stuff to the site. > > Community-generated FAQ pages sound great, but > > - Some (standard? readily-available?) technology is needed to allow >people to add stuff without intervention from the site organise

Re: how to write a simple cat

At first, thanks to all of you about this nice insight into FP used programmers. It was really a suprise to me to see that that what Sven wrote seems to be easily understood. I would really like to see such code-snippets to found on a central site what about www.haskell.org ? I reread my book and

RE: how to write a simple cat

> I know, we all have something else to do than to take on extra > responsibilities. But if someone could donate an access to a > fast web server (mine is just too slow) then we could go > along Wiki-Wiki Web Server concepts > (http://c2.com:8080/WikiWikiWeb) and h

Re: how to write a simple cat

Keith Wansbrough wrote: > Sven Panne wrote: > > > > Don't fear! Mr. One-Liner comes to the rescue:;-) > > > > > >longerThan fn lenlim = readFile fn >>= lines .| filter (length .| (>lenlim)) >.| zip [1..] .| map (\(n,l) -> shows n ") " ++ l) .| unlines .| putStr > > Friedrich wrote: > > >

Re: how to write a simple cat

> Date: Tue, 01 Jun 1999 17:32:22 +0200 > From: Sven Panne <[EMAIL PROTECTED]> > Don't fear! Mr. One-Liner comes to the rescue:;-) > >longerThan fn lenlim = readFile fn >>= lines .| filter (length .| (>lenlim)) .| >zip [1..] .| map (\(n,l) -> shows n ") " ++ l) .| unlines .| putStr Are

Re: how to write a simple cat

Sven Panne wrote: > > Don't fear! Mr. One-Liner comes to the rescue:;-) > > > >longerThan fn lenlim = readFile fn >>= lines .| filter (length .| (>lenlim)) .| >zip [1..] .| map (\(n,l) -> shows n ") " ++ l) .| unlines .| putStr Friedrich wrote: > Do you want to drive me away from lear

Re: how to write a simple cat

Sven Panne wrote: > > Friedrich Dominicus wrote: > >[...] How can I combine the output with a line-number can I put that > > into the filter? Or do I have to found another solution? > > Don't fear! Mr. One-Liner comes to the rescue:;-) > >longerThan fn lenlim = readFile fn >>= lines .|

Re: how to write a simple cat

Friedrich Dominicus wrote: >[...] How can I combine the output with a line-number can I put that > into the filter? Or do I have to found another solution? Don't fear! Mr. One-Liner comes to the rescue:;-) longerThan fn lenlim = readFile fn >>= lines .| filter (length .| (>lenlim)) .| zip

Re: how to write a simple cat

Keith Wansbrough wrote: > > Sven Panne wrote: > > > > Don't fear! Mr. One-Liner comes to the rescue:;-) > > > > > >longerThan fn lenlim = readFile fn >>= lines .| filter (length .| (>lenlim)) >.| zip [1..] .| map (\(n,l) -> shows n ") " ++ l) .| unlines .| putStr > > Friedrich wrote: >

Re: how to write a simple cat

Hannah Schroeter wrote: > > Hello! > > On Tue, Jun 01, 1999 at 06:58:32AM +0200, Friedrich Dominicus wrote: > > [...] > > > I want to do the following, read a file line by line and finding out > > which line is longer than x-chars. I want to print out which lines are > > so long. I think that c

Re: how to write a simple cat

On Tue, 1 Jun 1999, Sven Panne wrote: > Friedrich Dominicus wrote: > >[...] How can I combine the output with a line-number can I put that > > into the filter? Or do I have to found another solution? > > Don't fear! Mr. One-Liner comes to the rescue:;-) How about initiating Haskel

Re: how to write a simple cat

It would be nice if the prelude defined more general functions like: > splitStr c s = left:case right of [] -> []; otherwise -> splitStr c (tail right) > where (left,right)=span (/=c) s > joinStr c l = case l of []-> []; otherwise -> foldl1 (\x y->x++c:y) l The implementation of lines and unli

Re: how to write a simple cat

Hannah Schroeter wrote: > [...] So, still no need to fuzz with file handles :-) ... and no need to fuzz with intermediate names, either. :-) If you define an operator for reversed function composition (.|) = flip (.) and read it like a pipe in *nix, you get a one-liner: longerThan fn len

Re: how to write a simple cat

Hello! On Tue, Jun 01, 1999 at 06:58:32AM +0200, Friedrich Dominicus wrote: > [...] > I want to do the following, read a file line by line and finding out > which line is longer than x-chars. I want to print out which lines are > so long. I think that can just be done line-wise. > Thanks for yo

Re: how to write a simple cat

Hannah Schroeter wrote: > > Hello! > > On Mon, May 31, 1999 at 06:01:31PM +0200, Friedrich Dominicus wrote: > > Hannah Schroeter wrote: > > > > Hello! > > > > On Fri, May 28, 1999 at 08:00:27AM +0200, Friedrich Dominicus wrote: > > > > I wrote before with my trouble understanding hugsIsEOF. Bu

Re: how to write a simple cat

Hello! On Mon, May 31, 1999 at 06:01:31PM +0200, Friedrich Dominicus wrote: > Hannah Schroeter wrote: > > Hello! > > On Fri, May 28, 1999 at 08:00:27AM +0200, Friedrich Dominicus wrote: > > > I wrote before with my trouble understanding hugsIsEOF. But I don't have > > > found a clean way just t

Re: how to write a simple cat

Hannah Schroeter wrote: > > Hello! > > On Fri, May 28, 1999 at 08:00:27AM +0200, Friedrich Dominicus wrote: > > I wrote before with my trouble understanding hugsIsEOF. But I don't have > > found a clean way just to write a cat. Can s.o give me a hand? > > import System(getArgs) > file2stdout ::

Re: how to write a simple cat

On Fri, May 28, 1999 at 04:00:27PM EST, Friedrich Dominicus wrote: > I wrote before with my trouble understanding hugsIsEOF. But I don't have > found a clean way just to write a cat. Can s.o give me a hand? > Hi, You shouldn't need to use hugsIsEOF. Here's one possible implementation of a sim

Re: how to write a simple cat

module Main ( main ) where import IO import System main :: IO () main = do args <- getArgs s <- case args of []-> getContents [inF] -> readFile inF _ -> fail "Sorry, only 0 or 1 args implemented" putStr s --KW 8-) -

Re: how to write a simple cat

Hello! On Fri, May 28, 1999 at 08:00:27AM +0200, Friedrich Dominicus wrote: > I wrote before with my trouble understanding hugsIsEOF. But I don't have > found a clean way just to write a cat. Can s.o give me a hand? import System(getArgs) file2stdout :: String {- filename -} -> IO () file2stdout