- Haskell-Cafe - Haskell.org

10 PhD studentships in Nottingham
by Graham Hutton 02 Dec '21

02 Dec '21

Dear all, The School of Computer Science at the University of Nottingham in the UK is seeking applications for 10 fully-funded PhD studentships: https://tinyurl.com/ten-phd-2021 Applicants in the area of the Functional Programming Lab (tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor as soon as possible; the application deadline is 13th Feb: Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Graham Hutton - functional programming, haskell, category theory, program verification, program calculation. Nicolai Kraus - homotopy type theory, higher category theory, constructive mathematics, and related topics. The studentships are open to applicants of any nationality. Best wishes, Graham Hutton +-----------------------------------------------------------+ 10 Fully-Funded PhD Studentships School of Computer Science University of Nottingham, UK tinyurl.com/ten-phd-2021 Applications are invited from international and home students for 10 fully-funded PhD studentships offered by the School of Computer Science, starting on 1st October 2022. The topics for the studentships are open, but should relate to interests of one of the School's research groups: Computational Optimisation and Learning; Computer Vision; Cyber Security; Functional Programming; Intelligent Modelling and Analysis; Mixed Reality; Uncertainty in Data and Decision Making. The studentships are fully-funded for 3.5 years and include a stipend of £15,009 per year and tuition fees. Applicants are normally expected to have a first class bachelors or masters degree in Computer Science or another relevant area, and must obtain the support of a potential supervisor in the School prior to submitting their application. If you are interested in applying, please contact a potential supervisor as soon as possible, and at least two weeks prior to the closing date. If the supervisor wishes to support your application, they will direct you to make an official application through the MyNottingham system. Closing date for applications: Sunday 13th February 2022. +-----------------------------------------------------------+ 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 1.24
by Simon Michael 02 Dec '21

02 Dec '21

I am pleased to announce hledger 1.24! https://hledger.org/release-notes.html#hledger-1-24 Highlights include new report layout options with less eliding, hledger-ui mouse support, and many fixes and improvements. Thank you to release contributors Stephen Morgan, toonn, Pranesh Prakash, Dmitry Astapov, ShrykeWindgrace, Joaquin Azcarate, and Lawrence Wu. hledger (https://hledger.org) is a dependable, cross-platform "plain text accounting" tool, with command-line, terminal and web interfaces. It is an actively maintained, largely compatible reimplementation of Ledger CLI with many improvements. You can use it to track money, time, investments, cryptocurrencies, inventory and more. See also the Plain Text Accounting site (https://plaintextaccounting.org) https://hledger.org/download shows all the ways to install hledger on mac, windows or unix (stack, cabal, brew, nix, CI binaries, your package manager..). Or, run this bash script to install or upgrade to the latest release: $ curl -sO https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… $ less hledger-install.sh # security review $ bash hledger-install.sh New users, check out https://hledger.org/quickstart or the tutorials (with pictures) at hledger.org -> FIRST STEPS or the https://hledger.org/videos.html. To get help, see https://hledger.org#help, and join our chat via Matrix: - #hledger:matrix.org (http://matrix.hledger.org) or Libera (they are bridged): - #hledger:libera.chat (http://irc.hledger.org) Beginners and experts, contributors, sponsors, and all feedback are most welcome. Wishing you health and prosperity, -Simon

1 0

What is Data.Vec.DataFamily.SpineStrict.Pigeonhole and why is it following me?
by Galaxy Being 01 Dec '21

01 Dec '21

Spam detection software, running on the system "mail.haskell.org", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: This <https://hackage.haskell.org/package/vec-0.4/docs/Data-Vec-DataFamily-SpineS…> in Hackage is something a rank amateur like me can't fathom. I just hit a chapter in a book that dives into the Pigeonhole Principle. Is this the "accompanying Haskell Wundercode" for the math world's PHP? I know PHP is a big deal in math. I don't see an "author," and I see no documentation. Anyone know how I can figure this mystery out, like at least find the author or someone that knows something about this? [...] Content analysis details: (5.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (borgauf[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.0 BAYES_40 BODY: Bayes spam probability is 20 to 40% [score: 0.3039] 5.0 UNWANTED_LANGUAGE_BODY BODY: Message written in an undesired language 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid The original message was not completely plain text, and may be unsafe to open with some email clients; in particular, it may contain a virus, or confirm that your address can receive spam. If you wish to view it, it may be safer to save it to a file and open it with an editor.

3 2

MonadFail with type parameter for error message
by Daneel Yaitskov 30 Nov '21

30 Nov '21

Dear Cafe, MonadFail.fail takes String. I wasn't able to find MonadFail for custom error type. Is there any proposals to base? Let's say Data.Text, which gains popularity with OverloadedStrings extensions. class MonadFail m where fail :: String -> m a Why not ? class MonadFail m where fail :: (forall s. IsString s => s) -> m a class MonadFailWith m s where fail :: s -> m a -- Best regards, Daniil Iaitskov

3 3

Re: [Haskell-cafe] methods/tools for reading/presenting (time/allocation) profiling information?
by Olaf Klinke 26 Nov '21

26 Nov '21

> Dear Cafe, > > with +RTS -p -RTS, the resulting .prof file > shows (in the second part) what the expensive functions are. > (counting sections as GHC docs do - > first part gives program name and options) > > Often, that's useful, but sometimes, this info does not surprise me - > some things just don't have an easy implementation. > For those, I want to find out who calls them - > to possibly replace some of these calls > with a cheaper implementation (that is only valid > because the caller knows something that the callee does not) > > Is there some automation for getting this information? > I am not even sure how to formalize what I want. > Perhaps, for the first N heavy cost centers (SCCs), > a suitably ordered list of their callers (that inherit the cost)? > > The data is in the third (long, detailed) part of the .prof file > but I find it hard to process (in that form). It represents > the call hiearchy by indentation (first column) and adjacency (of rows) > but this goes out the window as soon as I grep or sort the rows. > > The JSON output format seems the way to go > https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.h… > . > Yeah, I should probably just aeson it and then walk the tree. > I still wanted to ask for advice first, or references > to existing work. Any pointers appreciated. > > - J. > Profiteur has served me well in this regard. It shows me what top-level functions eat most of the execution times, and which sub-functions have the biggest share thereof, etc. All in a nice interactive browser interface. https://hackage.haskell.org/package/profiteur Olaf

1 0

methods/tools for reading/presenting (time/allocation) profiling information?
by Johannes Waldmann 25 Nov '21

25 Nov '21

Dear Cafe, with +RTS -p -RTS, the resulting .prof file shows (in the second part) what the expensive functions are. (counting sections as GHC docs do - first part gives program name and options) Often, that's useful, but sometimes, this info does not surprise me - some things just don't have an easy implementation. For those, I want to find out who calls them - to possibly replace some of these calls with a cheaper implementation (that is only valid because the caller knows something that the callee does not) Is there some automation for getting this information? I am not even sure how to formalize what I want. Perhaps, for the first N heavy cost centers (SCCs), a suitably ordered list of their callers (that inherit the cost)? The data is in the third (long, detailed) part of the .prof file but I find it hard to process (in that form). It represents the call hiearchy by indentation (first column) and adjacency (of rows) but this goes out the window as soon as I grep or sort the rows. The JSON output format seems the way to go https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.h… . Yeah, I should probably just aeson it and then walk the tree. I still wanted to ask for advice first, or references to existing work. Any pointers appreciated. - J.

2 1

Logging
by Olaf Klinke 22 Nov '21

22 Nov '21

Dear Hilco, attached is a module we use in production. It builds on top of the monad-logger package which is used, among other places, in Yesod. Olaf

1 0

Re: [Haskell-cafe] Logging
by Olaf Klinke 22 Nov '21

22 Nov '21

As someone who works with timeseries for a living, I can say that what is a nightmare is timestamps that do not correspond to a unique UTC time. So you'd want a ZonedTime timestamp. I've been using monad-logger and rolled my own extension which adds (formatted) time stamps to the log messages. Olaf

1 0

Locate errors in TH for Haskell code
by Anton Kholomiov 21 Nov '21

21 Nov '21

I have a task to convert one Haskell expression to another. And I'd like to report errors properly. [interpret| -- error reported here valid haskell code invalid code <- error |] I can parse it with haskell-src-exts or haskell-src-meta. but if I have error in the code (type-check) error is positioned on the first line of the QQ-expression. Do you know is it possible to report error at the line where it has happened or to keep original source code location in the Exp. In the function I do transformation Exp -> Exp. Or maybe there is a better way to do it instead of QQ?

4 4

Re: [Haskell-cafe] code in postings mangled?
by Olaf Klinke 19 Nov '21

19 Nov '21

> Why is code in postings so often mangled: > Seems it is only the linebreaks. Some programs on Windows, including TextEdit and likely your mail client, don't consider a newline '\n' character to be a line break, since Windows terminates lines by "\r\n". Then OS X has '\r' line terminators, which again might not be considered a linebreak on some systems. I remember all kinds of stupid things arising from this, including version control systems flagging every line as changed when it was only the line breaks. I read this list as digest, so I can not verify using the particular raw email you quoted. Can someone else check this? Regards, Olaf

2 1