- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Faster set intersections?
by Doug McIlroy 10 Dec '18

10 Dec '18

> The following expressions both cause GHCI to hang: > > S.intersection (S.fromList [1,2]) (S.fromList [1..]) > S.intersection (S.fromList [1..]) (S.fromList [1,2]) > > Is there a smarter way to take the intersection of sets when at least one > of them is small (but I don't know which one that is)? "Small" is not enough. If all you know is that the lists represent sets of integers, then S.intersection (S.fromList [-1,-2]) (S.fromList [1..]) must diverge. A sufficient condition for success in such examples is that the sets come from a well-ordered domain and are presented in order. Then it's easy to write a merge-like algorithm. Both sets can be infinite; every finite prefix of the intersection will eventually appear. (Note that the integers are not well-ordered, though the positive integers are.) Doug

2 1

Faster set intersections?
by Jeffrey Brown 09 Dec '18

09 Dec '18

The following expressions both cause GHCI to hang: > S.intersection (S.fromList [1,2]) (S.fromList [1..]) fromList ^CInterrupted. > S.intersection (S.fromList [1..]) (S.fromList [1,2]) fromList ^CInterrupted. > Is there a smarter way to take the intersection of sets when at least one of them is small (but I don't know which one that is)? -- Jeff Brown | Jeffrey Benjamin Brown Website <https://msu.edu/~brown202/> | Facebook <https://www.facebook.com/mejeff.younotjeff> | LinkedIn <https://www.linkedin.com/in/jeffreybenjaminbrown>(spammy, so I often miss messages here) | Github <https://github.com/jeffreybenjaminbrown>

6 5

Stack data structure
by daniel huebleitner 08 Dec '18

08 Dec '18

I am a graduate student in theoretical computer science playing around with haskell for the past year or so. I wrote a Stack Data structure today and would like to get some feedback from more experienced haskellers if possible. I know its a really simple thing to write. But the implementation I found on hackage wasn't what I was looking for. I haven't wrote unit tests yet, but it should behave as expected. Thanks in advance. Kind regards. Daniel

5 5

Re: [Haskell-cafe] [Haskell] Guidelines for respectful communication
by Dan Burton 07 Dec '18

07 Dec '18

Thank you, Simon. My experience with the Haskell community has been quite positive over the years. I am continually pleased to see community leaders make an intentional effort to maintain the Haskell community's reputation of kindness, helpfulness, and inclusiveness. Say what you will about design-by-committee processes, but the growing Haskell community -- with the increasing diversity that comes with that -- is refining, extending, and supporting the language in new and interesting ways. By intentionally and explicitly embracing these patterns of respectful communication, you facilitate the continued growth and improvement of the language. Thank you again for the careful thought you have put into the topic of communication. Your effort is greatly appreciated! -- Dan Burton On Thu, Dec 6, 2018 at 5:35 AM Simon Peyton Jones via Haskell < haskell(a)haskell.org> wrote: > Friends > As many of you will know, I have been concerned for several years about > the standards of discourse in the Haskell community. I think things have > improved since the period that drove me to write my Respect email< > https://mail.haskell.org/pipermail/haskell/2016-September/024995.html>, > but it's far from secure. > We discussed this at a meeting of the GHC Steering Committee< > https://github.com/ghc-proposals/ghc-proposals> at ICFP in September, and > many of us have had related discussions since. Arising out of that > conversation, the GHC Steering Committee has decided to adopt these > Guidelines for respectful communication< > https://github.com/ghc-proposals/ghc-proposals/blob/master/GRC.rst> > > We are not trying to impose these guidelines on members of the Haskell > community generally. Rather, we are adopting them for ourselves, as a > signal that we seek high standards of discourse in the Haskell community, > and are willing to publicly hold ourselves to that standard, in the hope > that others may choose to follow suit. > We are calling them "guidelines for respectful communication" rather than > a "code of conduct", because we want to encourage good communication, > rather than focus on bad behaviour. Richard Stallman's recent post< > https://lwn.net/Articles/769167/> about the new GNU Kind Communication > Guidelines<https://gnu.org/philosophy/kind-communication.html> expresses > the same idea. > Meanwhile, the Stack community is taking a similar approach< > https://www.snoyman.com/blog/2018/11/proposal-stack-coc>. > Our guidelines are not set in stone; you can comment here< > https://github.com/ghc-proposals/ghc-proposals/commit/373044b5a78519071b9a2…>. > Perhaps they can evolve so that other Haskell committees (or even > individuals) feel able to adopt them. > The Haskell community is such a rich collection of intelligent, > passionate, and committed people. Thank you -- I love you all! > Simon > > > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell >

2 1

Fwd: [Fp-nl] FP-Day 2019
by Bas Lijnse 06 Dec '18

06 Dec '18

Hi Haskell-Cafe This is probably only relevant for (but not exclusively for) the Haskellers from the Netherlands. I just wanted to make you aware of the upcoming Dutch FP-Day on January 11, 2019. Best, Bas -------- Forwarded Message -------- Subject: [Fp-nl] FP-Day 2019 Date: Mon, 3 Dec 2018 20:24:37 +0100 From: Bas Lijnse via Fp-nl <fp-nl(a)lists.science.uu.nl> Reply-To: Bas Lijnse <bas(a)baslijnse.nl> To: fp-nl(a)lists.science.uu.nl Dear Fellow Functional Programmers, As the end of 2018 is rapidly approaching, you may be wondering when and where the Dutch FP-Day 2019 will be. It is traditionally organized one of the first Fridays of the new year after all. We have the pleasure to announce that it will be on *Friday Jan 11, 2019* in *Breda*. It will be hosted by the Netherlands Defence Academy at the "Trip van Zoutlandt Kazerne". More information about registration, the program and other details can be found at: https://wiki.clean.cs.ru.nl/NL-FP_dag_2019 You can register, and/or propose a talk by e-mailing us directly (because of the venue, registration is mandatory). Best regards, Bas Lijnse and Jan Martin Jansen b.lijnse(a)mindef.nl / b.lijnse(a)cs.ru.nl jm.jansen.04(a)mindef.nl / jan.martin.jansen(a)gmail.com PS. Apologies if you receive this e-mail twice. It came to our attention that an earlier attempt of sending this e-mail to this list failed somehow. _______________________________________________ Fp-nl mailing list Fp-nl(a)lists.science.uu.nl https://mailman.science.uu.nl/mailman/listinfo/fp-nl

1 0

ghc install from source fails
by Branimir Maksimovic 06 Dec '18

06 Dec '18

I have this problem when installin ghc from git: nstalling library in /home/bmaxa/ghc/lib/ghc-8.7.20181205/ghc-prim-0.5.3 dist-install/build/HSghc-prim-0.5.3.p_o: copyFile: does not exist (No such file or directory) p_o files are missing, and install fails. google does not helps. Can't find any option to suppress installation of p_o files or to build them. Thanks, Branimir.

1 0

Fwd: [Haskell-beginners] Database simple-mysql
by Damien Mattei 05 Dec '18

05 Dec '18

-------- Message transféré -------- Sujet : [Haskell-beginners] Database simple-mysql Date : Wed, 5 Dec 2018 11:29:30 +0100 De : Damien Mattei <mattei(a)oca.eu> Répondre à : The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners(a)haskell.org> Pour : beginners(a)haskell.org why does this works: let name = "'A 20'" bd_rows <- query_ conn "select `N° BD` from sidonie.Coordonnées where Nom = 'A 20'" putStrLn $ show bd_rows putStrLn $ show name i got: [Only {fromOnly = "-04.3982"}] "'A 20'" -04.3982 but not with this: bd_rows <- query conn "select `N° BD` from sidonie.Coordonnées where Nom = ?" (Only (name::String)) i got an empty result: [] ... ??? -- Damien.Mattei(a)unice.fr, Damien.Mattei(a)oca.eu, UNS / OCA / CNRS _______________________________________________ Beginners mailing list Beginners(a)haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

2 1

Re: [Haskell-cafe] static analysis of a C-like language
by Olaf Klinke 04 Dec '18

04 Dec '18

> Hello Olaf, > > to me that sounds as if you want to do an abstract interpretation with a > forward collecting semantics that employs non-relational abstract > domains for the primitive data types and summarizes the dimensions of > arrays. ... > I would start by writing a simple interpreter for the language to be > analyzed. That way you fix messy details before they bite you, e.g. the > order in which submodules are loaded and initialized. I was hoping not having to write an interpreter (because the language author wrote a translation to C++ already), but if that is the way to go, I'll do it. As I understand it, the Haskell semantics should contain just enough substance so that the errors I am after will cause hiccups in the Haskell compiler? That is indeed a compelling approach. What this does not address is the question about error reporting: How could a translation to Haskell preserve information about scope, source position and masking? Can I leverage the ghc API for that? Regards, Olaf

3 2

10 PhD studentships in Nottingham
by Graham Hutton 04 Dec '18

04 Dec '18

Dear all, The School of Computer Science at the University of Nottingham is seeking applications for 10 fully-funded PhD studentships: https://tinyurl.com/10-phds-2019 Applicants in the area of the Functional Programming Laboratory (https://tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor at least two weeks prior to the 18th January deadline: Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Venanzio Capretta - type theory, mathematical logic, corecursive structures, proof assistants, category theory, epistemic logic. Graham Hutton - functional programming, program calculation and transformation, correctness and efficiency, category theory. Henrik Nilsson - functional reactive programming, modelling and simulation, domain-specific languages, probabilistic languages. Best wishes, Graham +-----------------------------------------------------------+ 10 Fully-Funded PhD Studentships School of Computer Science University of Nottingham, UK https://tinyurl.com/10-phds-2019 Applications are invited for up to ten fully-funded PhD studentships in the School of Computer Science at the University of Nottingham, starting on 1 October 2019. The topics for the studentships are open, but should relate to one of the School’s research groups: Agents Lab; Automated Scheduling and Planning; Computer Vision Lab; Data Driven Algorithms, Systems and Design; Functional Programming Lab; Intelligent Modelling and Analysis; Uncertainty in Data and Decision Making; Mixed Reality Lab. The studentships are for a minimum of three years and include a stipend of £14,777 per year and tuition fees. They are open to students of any nationality. Applicants are normally expected to have a first-class MSc or BSc in Computer Science or a related discipline, and must obtain the support of a supervisor in the School prior to submitting their application. Initial contact with supervisors should be made at least two weeks prior to the closing date for applications. Informal enquiries may be addressed to SS-PGR-JC(a)nottingham.ac.uk. To apply, please submit the following items by email to: Christine.Fletcher(a)nottingham.ac.uk: (1) a brief covering letter that describes your reasons for wishing to pursue a PhD, your proposed research area and topic, and the name of the potential supervisor whose support you have already secured; (2) a copy of your CV, including your actual or expected degree classes, and results of all University examinations; (3) an extended example of your technical writing, such as a project report or dissertation; (4) contact details for two academic referees. Closing date for applications: Friday 18 January 2019 +-----------------------------------------------------------+ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

1 0

ANN: hledger-1.12
by Simon Michael 03 Dec '18

03 Dec '18

hledger is a robust, cross-platform plain text accounting tool, for tracking money, time, stocks, cryptocurrencies or any other commodity, using double-entry accounting, private or shared plain text files, revision control, and command-line, curses or web UIs. Find out more at http://hledger.org and http://plaintextaccounting.org. I'm pleased to announce the release of hledger 1.12! Thank you release contributors Alex Chen, Jesse Rosenthal, Samuel May, Mykola Orliuk, Peter Simons, Moritz Kiefer, Dmitry Astapov, Felix Yan, Aiken Cairncross, and Nikhil Jha. After two years of regular quarter-end releases, I am speeding up hledger's release cadence: we now aim to release every 1-3 months, as needed or wanted, with our normal release window being the first few days of each month. Release notes (http://hledger.org/release-notes) ------------------------------------------------- hledger 1.12 * install script: ensure a new-enough version of stack; more informative output * build with GHC 8.6/base-4.12 (Peter Simons) * add required upper bound for statistics (Samuel May) * --anon anonymises more thoroughly (including linked original postings) (Moritz Kiefer) * unbalanced transaction errors now include location info (Mykola Orliuk) * accounts command: --drop also affects the default flat output, without needing an explicit --flat flag * accounts command: the --codes flag has been dropped * accounts command: filtering by non-account-name queries now works * add command: fix transaction rendering regression during data entry and in journal file * balance command: fix wrongful eliding of zero-balance parent accounts in tree mode (Dmitry Astapov) * journal format, bs/bse/cf/is commands: account directives can declare account types (#877) Previously you had to use one of the standard english account names (assets, liabilities..) for top-level accounts, if you wanted them to appear in the right place in the balancesheet, balancesheetequity, cashflow or incomestatement reports. Now you can use your preferred account names, and use account directives to declare which accounting class (Asset, Liability, Equity, Revenue or eXpense) an account (and its subaccounts) belongs to, by writing one of the letters A, L, E, R, X after the account name, after two or more spaces. This syntax may change (see issue). Experimental. Currently we allow unlimited account type declarations anywhere in the account tree. So you could declare a liability account somewhere under assets, and maybe a revenue account under that, and another asset account even further down. In such cases you start to see oddities like accounts appearing in multiple places in a tree-mode report. I have left it this way for now in case it helps with, eg, modelling contra accounts, or combining multiple files each with their own account type declarations. (In that scenario, if we only allowed type declarations on top-level accounts, or only allowed a single account of each type, complications seem likely.) * journal format: periodic transaction rules now require a double space separator. In periodic transaction rules which specify a transaction description or same-line transaction comment, this must be separated from the period expression by two or more spaces, to prevent ambiguous parsing. Eg this will parse correctly as "monthly" thanks to the double space: ~ monthly In 2020 we'll end this monthly transaction. * journal format: exact/complete balance assertions (Samuel May). A stronger kind of balance assertion, written with a double equals sign, asserts an account's complete account balance, not just the balance in one commodity. (But only if it is a single-commodity balance, for now.) Eg: 1/1 (a) A 1 (a) B 1 (a) 0 = A 1 ; commodity A balance assertion, succeeds (a) 0 == A 1 ; complete balance assertion, fails * journal format: account directives now allow whitespace or a comment after the account name * journal format: using ~ for home directory in include directives now works (#896) (Mykola Orliuk) * journal format: prevent misleading parse error messages with cyclic include directives (#853) (Alex Chen) * journal format: transaction modifier multipliers handle total-priced amounts correctly (#928). Multipliers (*N) in transaction modifier rules did not multiply total-priced amounts properly. Now the total prices are also multiplied, keeping the transaction balanced. * journal format: do amount inference/balance assignments/assertions before transaction modifiers (#893, #908) (Jesse Rosenthal) Previously, transaction modifier (auto postings) rules were applied before missing amounts were inferred. This meant amount multipliers could generate too many missing-amount postings, making the transaction unbalanceable (#893). Now, missing amount inference (and balance assignments, and balance assertions, which are interdependent) are done earlier, before transaction modifier rules are applied (#900, #903). Also, we now disallow the combination of balance assignments and transaction modifier rules which both affect the same account, which could otherwise cause confusing balance assertion failures (#912). (Because assignments now generate amounts to satisfy balance assertions before transaction modifier rules are applied (#908).) * journal format: periodic transaction rules are now aware of Y default year directives. (#892) Ie when a default year Y is in effect, they resolve partial or relative dates using Y/1/1 as the reference date, rather than today's date. hledger-ui 1.12 * fix "Any" build error with GHC < 8.4 * error screen: always show error position properly (#904) (Mykola Orliuk) * accounts screen: show correct balances when there's only periodic transactions * drop the --status-toggles flag * periodic transactions and transaction modifiers are always enabled. Rule-based transactions and postings are always generated (--forecast and --auto are always on). Experimental. * escape key resets to flat mode. Flat mode is the default at startup. Probably it should reset to tree mode if --tree was used at startup. * tree mode tweaks: add --tree/-T/-F flags, make flat mode the default, toggle tree mode with T, ensure a visible effect on register screen * hide future txns by default, add --future flag, toggle with F. You may have transactions dated later than today, perhaps piped from print --forecast or recorded in the journal, which you don't want to see except when forecasting. By default, we now hide future transactions, showing "today's balance". This can be toggled with the F key, which is easier than setting a date query. --present and --future flags have been added to set the initial mode. (Experimental. Interactions with date queries have not been explored.) * quick help tweaks; try to show most useful info first * reorganise help dialog, fit content into 80x25 again * styling tweaks; cyan/blue -> white/yellow * less noisy styling in horizontal borders (#838) * register screen: positive amounts: green -> black The green/red scheme helped distinguish the changes column from the black/red balance column, but the default green is hard to read on the pale background in some terminals. Also the changes column is non-bold now. Getting started: ---------------- All install methods are described at http://hledger.org/download . You can download windows binaries, or use a package manager, though in some cases these will install an older hledger version. You can build the latest hledger packages with stack: $ stack install --resolver=lts-12 megaparsec-7.0.4 cassava-megaparsec-2.0.0 config-ini-0.2.3.0 hledger-lib-1.12 hledger-1.12 [hledger-ui-1.12] [hledger-web-1.12] [hledger-api-1.12] or with cabal: $ cabal update && cabal install hledger-1.12 [hledger-ui-1.12] [hledger-web-1.12] [hledger-api-1.12] or with the hledger installer, on systems with bash installed (handy if you don't have a working stack or cabal): $ curl -s https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… > hledger-install.sh $ less hledger-install.sh # satisfy yourself that the script is safe $ bash hledger-install.sh Some commands to try: $ hledger add # record some transactions, with guidance $ hledger print # show recorded transactions $ hledger balance # show totals by account $ hledger -h # show quick help $ hledger # list available commands $ hledger help # list built-in manuals To get oriented, see the tutorials and manuals at http://hledger.org ; say hello and ask questions in the #hledger IRC channel on Freenode, accessible at http://irc.hledger.org . New users and contributors are always welcome! Best, -Simon

1 0