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Re: interrupts
by Doug McIlroy 05 Aug '09

05 Aug '09

I got my answer about interrupts. Very basic indeed. No more answers needed.

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interrupts
by Doug McIlroy 05 Aug '09

05 Aug '09

Very basic question about Winhugs: How to interrupt a computation?

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How to print table data in a format and than query it
by napster007 02 Jun '09

02 Jun '09

This part is about embedding a simple query in Haskell. In this assignment you are specifically required to exploit Haskell's predefined higher-order functions. You can use the following Higher Order Functions: map, filter, zipWith, any, all, takeWhile, dropWhile You can represent a database table with a value of this type: data Table = Table String --table name [String] --field names [[String]] --records Suppose now we have a value Table n s z. It represents a table whose name is n; s specifies the names of the columns in the table; and z is a list of the records in the table. To keep it simple, you can represent all those values using plain string Below is the table represented in that way. The table contains data about the top-10 Largest Countries in the world with its corresponding area given in square kilometers. top10 = Table "LargestCountries" [ "Rank","Country", "Area"] [ [ "1", "Russia", "17,075,400"] , [ "2", "Canada", "9,976,140"] , [ "3", "United States", "9,629,091"] , [ "4", "China", "9,596,960"] , [ "5", "Brazil", "8,511,965"] , [ "6", "Australia", "7,686,850"] , [ "7", "India", "3,287,590"] , [ "8", "Argentina", "2,776,890"] , [ "9", "Kazakhstan", "2,717,306"] , [ "10", "Sudan", "2,505,810"] ] The functionalities that you must implement are listed below: 1. Show a table: write a function that formats a row, and then maps this function over a table to format the table. 2. Project a table: write a function that projects a row, and then maps this function over a table to project the table. 3. Select from a table: write a function that determines whether a row satisfies the given selection criteria, then filter the table using this function. Functionality 1: Show a Table You cannot unfortunately view a table (yet), for example, try to type top10 in hugs. Hugs will complain that it does not know how to show a table. So, this is your first task. Write a function printTable::Table->IO() that can nicely print a table like below: LargestCountries: |Rank|Country |Area | ------------------------------------- |1 |Russia |17,075,400 | |2 |Canada |9,976,140 | |3 |United States |9,639,091 | |4 |China |9,596,960 | |5 |Brazil |8,511,965 | |6 |Australia |7,686,850 | |7 |India |3,287,590 | |8 |Argentina |2,776,890 | |9 |Kazakhstan |2,717,306 | |10 |Sudan |2,505,810 | It will be easier if you first write: writeTable::Table->String which simply converts a table to a flat string, and then printTable is simply: printTable=putStr.writeTable Write your solution modularly. Small sub-functionalities which are used repeatedly are best implemented as separate functions, so you can reuse them in multiple places. Functionality 2: Select Columns The next operation you must implement is so-called projection. That is, getting a selected set of columns from a table. Consider a function project with the following type: project::[String]->Table->Table The application project fields table returns a new table consisting of only the columns from the original table whose names is specified in fields. So, for example, printTable.project["Rank", "Country"]$top10 will produce the following table: LargestCountries: |Rank|Country | ------------------------ |1 |Russia | |2 |Canada | |3 |United States | |4 |China | |5 |Brazil | |6 |Australia | |7 |India | |8 |Argentina | |9 |Kazakhstan | |10 |Sudan | Your task is to implement this function project. Functionality 3: Select Records The next operation is used to select rows (records) from a database. Consider a function select with the following type: select::String->(String->Bool)->Table->Table The application select field p table will return a new table, containing only the rows r from the original table such that the value of r at column field satisfies the predicate p. Here is an example: printTable.select "Rank" p $ top10 where p x = read x < (6::Int) will produce the following table: LargestCountries: |Rank|Country |Area | ------------------------------------- |1 |Russia |17,075,400 | |2 |Canada |9,976,140 | |3 |United States |9,639,091 | |4 |China |9,596,960 | |5 |Brazil |8,511,965 | Implement the function select. -- View this message in context: http://www.nabble.com/How-to-print-table-data-in-a-format-and-than-query-it… Sent from the Haskell - Hugs-Users mailing list archive at Nabble.com.

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Trying to uninstall
by David 24 Feb '09

24 Feb '09

I'm trying to uninstall Hugs for Windows (ver. "Sep 2006"), but when I run the uninstaller, I get the following error message: The NTVDM CPU has encountered an illegal instruction. CS:0eab IP:0130 OP:63 6f 6e 74 65 Choose 'Close' to terminate the application. How can I cleanly uninstall Hugs? I tried the "add/remove" option in the Windows control panel, but got the same error. Can I simply delete the directory where it was installed, or is it messier than that? Are there entries in the Windows registry that need to be removed? Thanks.

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New Hugs custom snapshot available
by Dimitry Golubovsky 17 Feb '09

17 Feb '09

Hi, I have uploaded a new custom snapshot of Hugs which is available at this link: http://corehugs.googlecode.com/files/hugs-2009-02-16.tar.gz Results of "make LibStatus" are here: http://corehugs.googlecode.com/files/LibStatus-2009-02-16 This snapshot was built with the version 1.0.0.2 of the "directory" package taken from the GHC 6.10 branch. The reason for this: head version of System.Directory became incompatible with Hugs, likely after the NHC integration patch. This patch was not applied to the GHC 6.10 branch before tagging 1.0.0.2. Ther rest of packages are from the head, plus several packages necessary to use the Yhc Core tools were added to the snapshot. Thanks. -- Dimitry Golubovsky Anywhere on the Web

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FFI static linking
by Fernan Bolando 17 Nov '08

17 Nov '08

Hi Is it possible to do static link on module that uses ffi interface? I am trying to make the ffi interface work Plan9, which doesnt have dynamic loading. ffihugs crashes when I try to create a module. It is probably due to the hugs port, but wanted to get your opinions. thanks fernan -- http://www.fernski.com

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How to getCh on MS Windows command line?
by Ahn, Ki Yung 10 Nov '08

10 Nov '08

What I mean by getCh is the non-buffered non-echoed version of getChar, which Hugs used to provided as an extension but not any more. Is there any way to have a non-buffered non-echoed single character input function on MS Windows command line using only the libraries in the MS Windows distribution packages of either GHC or Hugs? The reason to why this is important for me is because I am translating Graham Hutton's "Programming in Haskell" into Korean (soon to be published), which illustrates interactive programming with the example of a calculator that responds instantly for every keystroke of numbers and arithmetic operations running on text mode. It is very important to consider the readers who only have access to MS Windows systems, because Korean OS market share is completely skewed towards MS Windows for very embarrassing reasons that I do not even want to mention. And, isn't GHC developed in MSR anyway? :-) I remember that this is an old problem for both of the two most widely used Haskell implementation, Hugs and GHC. In ghc 6.8 getChar had a bit strange behavior. As far as I remember it always worked as if it were NoBuffering. Fortunately, in the recently released ghc 6.10, this has been fixed. We now actually have to set the buffering mode to NoBuffering with hSetBufferring to get the non-buffered behavior of getChar. But, it still isn't working on MS Windows. In Hugs, hSetBuffering neither works on Unix terminal nor on MS Windows command line. Surprisingly, it works in WinHugs. However, I cannot use WinHugs for my purpose because the interactive calculator example in the book also uses beep characters and ANSI codes which do not work in WinHugs. Thanks for any hacks or suggestions, -- Ahn, Ki Yung

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hugs98 on macports
by Calum Robertson 07 Apr '08

07 Apr '08

Hi, I've installed hugs98 (version September 2006) using macports on Leopard and I'm having a few problems when I try to load code that contains: import Graphics.SOE (I'm typing in programs from the School of Expression book by Paul Hudak). I get the error: ERROR "/opt/local/lib/hugs/packages/HGL/Graphics/HGL/Internals/ Types.hs" - Can't find imported module "Graphics.X11.Xlib" Apart from this, Hugs seems to run okay. Any ideas on how to fix this? C

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wrong infered types?
by Paqui Lucio 11 Jan '08

11 Jan '08

Hi, In Hugs, the infered types for the following four functions: f a = let m = id a in do return m f' a = do m <- id a return m g a = let m =[a,a] in do return m g' a = do m <- [a,a] return m respectively are f :: Monad a => b -> a b f' :: Monad a => a b -> a b g :: Monad a => b -> a [b] g' :: a -> [a] I didn't expect this types, do you? Anybody has some explanation? Thanks in advance, Paqui --------------------------------- Paqui Lucio Dpto de LSI Facultad de Informática Paseo Manuel de Lardizabal, 1 20080-San Sebastián SPAIN --------------------------------- e-mail: paqui.lucio(a)ehu.es Tfn: (+34) (9)43 015049 Fax: (+34) (9)43 015590 Web: http://www.sc.ehu.es/paqui ---------------------------------

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A few comments on WinHugs-sep2006.exe
by Thorkil Naur 26 Oct '07

26 Oct '07

Hello, As an enthusiastic Hugs user, I recently installed Hugs using WinHugs-Sep2006.exe and noted the following: 1. When running hugs.exe from an ordinary DOS prompt, activating the editor (Notepad) using :e returns control immediately to the Hugs prompt, in addition to starting the Notepad. So, although I am able to edit the desired (Haskell) source file, I need to do a :r after saving, to make Hugs aware of the changes. This is certainly different from what I have experienced with earlier Hugs'es where :e did not return until edits were completed, enabling Hugs to respond to the most recent edits immediately. 2. Running hugs.exe from a DOS prompt reports the version as 20051031 whereas activating WinHugs reports Version Sep 2006. 3. In the WinHugs menu, the menu item Help has it's "l" underscored. Nevertheless, Alt-h is what is required to activate the help menu. I will gladly enter Hugs trac issues for these items if convenient. Thanks and best regards Thorkil

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