Below are the five most recent posts in my weblog. You can also see a chronological list of all posts, dating back to 1999.

When I did the work described earlier in template haskell, I also explored generic programming in Haskell to solve a particular problem. StrIoT is a program generator: it outputs source code, which may depend upon other modules, which need to be imported via declarations at the top of the source code files.

The data structure that StrIoT manipulates contains information about what modules are loaded to resolve the names that have been used in the input code, so we can walk that structure to automatically derive an import list. The generic programming tools I used for this are from Structure Your Boilerplate (SYB), a module written to complement a paper of the same name. In this code snippet, everything and mkQ are from SYB:

extractNames :: Data a => a -> [Name]
extractNames = everything (++) (\a -> mkQ [] f a)
     where f = (:[])

The input must be any type which implements typeclass Data, as must all its members (and their members etc.): This holds for the Template Haskell Exp types. The output is a normal list of Names. The utility function has a more specific type Name -> [Name]. This is all that's needed to walk over the heterogeneous data structures and do something specific (f) when we encounter a Name.

Post-processing the Names to get a list of modules is simple

 nub . catMaybes . map nameModule . concatMap extractNames

Unfortunately, there's a weird GHC behaviour relating to the module names for some Prelude functions that makes the above less useful in practice. For example, the Prelude function words :: String -> [String] can normally be used without an explicit import (since it's a Prelude function). However, once round-tripped through a Name, it becomes GHC.OldList.words. Attempting to import GHC.OldList fails in some contexts, because it's a hidden module or package. I've been meaning to investigate further and, if necessary, file a GHC bug about this.

For this reason I've scrapped all the above and gone with a different plan. We go back to requiring the user to specify their required import list explicitly. We then walk over the Exp data type prior to code generation and decanonicalize all the Names. I also use generic programming/SYB to do this:

unQualifyNames :: Exp -> Exp
unQualifyNames = everywhere (\a -> mkT f a)
     where f :: Name -> Name
           f n = if n == '(.)
            then mkName "."
            else (mkName . last . splitOn "." . pprint) n

I've had to special-case composition (.) since that code-point is also used as the delimiter between package, module and function. Otherwise this looks very similar to the earlier function, except using everywhere and mkT (make transformation) instead of everything and mkQ (make query).

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At the start of the year I begun keeping a daily diary for work as a simple text file. I've used various other approaches for this over the years, including many paper diaries and more complex digital systems. One great advantage of the one-page text file was it made assembling my weekly status report email very quick, nearly just a series of copies and pastes. But of course there are drawbacks and room for improvement.

vimwiki is a personal wiki plugin for the vim and neovim editors. I've tried to look at it before, years ago, but I found it too invasive, changing key bindings and display settings for any use of vim, and I use vim a lot.

I decided to give it another look. The trigger was actually something completely unrelated: Steve Losh's blog post "Coming Home to vim". I've been using vim for around 17 years but I still learned some new things from that blog post. In particular, I've never bothered to Use The Leader for user-specific shortcuts.

The Leader, to me, feels like a namespace that plugins should not touch: it's like the /usr/local of shortcut keys, a space for the local user only. Vimwiki's default bindings include several incorporating the Leader. Of course since I didn't use the leader, those weren't the ones that bothered me: It turns out I regularly use carriage return and backspace for moving the cursor around in normal mode, and Vimwiki steals both of those. It also truncates the display of (what it thinks are) URIs. It turns out I really prefer to see exactly what's in the file I'm editing. I haven't used vim folds since I first switched to it, despite them being why I switched.

Disabling all the default bindings and URI concealing stuff and Vimwiki is now much less invasive and I can explore its features at my own pace:

let g:vimwiki_key_mappings = { 'all_maps': 0, }
let g:vimwiki_conceallevel = 0
let g:vimwiki_url_maxsave = 0 

Followed by explicitly configuring the bindings I want. I'm letting it steal carriage return. And yes, I've used some Leader bindings after all.

nnoremap <leader>ww :VimwikiIndex<cr>
nnoremap <leader>wi :VimwikiDiaryIndex<cr>
nnoremap <leader>wd :VimwikiMakeDiaryNote<cr>

nnoremap <CR> :VimwikiFollowLink<cr>
nnoremap <Tab> :VimwikiNextLink<cr>
nnoremap <S-Tab> :VimwikiPrevLink<cr>
nnoremap <C-Down> :VimwikiDiaryNextDay<cr>
nnoremap <C-Up> :VimwikiDiaryPrevDay<cr>

,wd (my leader) now brings me straight to today's diary page, and I can create separate, non-diary pages for particular work items (e.g. a Ticket reference) that will span more than one day, and keep all the relevant stuff in one place.

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This is the tenth part in a series of blog posts. The previous post was Amiga floppy recovery project: what next?. The whole series is available here: Amiga.

Rotary encoder, OLED display and mount

Rotary encoder, OLED display and mount

I haven't made any substantive progress on my Amiga floppy recovery project for a while, but I felt like some retail therapy a few days ago so I bought a rotary encoder and OLED display for the Gotek floppy disk emulator along with a 3D-printed mount for them. I'm pleased with the results! The rather undescriptive "DSKA0001" in the picture is a result of my floppy image naming scheme: the display is capable of much more useful labels such as "Lemmings", "Deluxe Paint IV", etc.

The Gotek and all the new bits can now be moved inside the Amiga A500's chassis.

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Last Christmas, to make room for a tree, I dis-assembled my hifi unit and (temporarily, I thought) lugged my hi-fi and records up to the study.

Power, Corruption & Lies

I had been thinking about expanding the amount of storage I had for hifi and vinyl, perhaps moving from 2x2 storage cubes to 2x3, although Ikea don't make a 2x3 version of their stalwart vinyl storage line, the Kallax. I had begun exploring other options, both at Ikea and other places. Meanwhile, I re-purposed my old Expedit unit as storage for my daughter's Sylvanian Families.

Under Lockdown, I've spent a lot more time in my study, and so I've set up the hifi there. It turns out I have a lot more opportunity to enjoy the records up here, during work, and I've begun to explore some things which I haven't listened to in a long time, or possibly ever. I thought I'd start keeping track of some of them.

Power, Corruption and Lies is not something rarely listened to. It's steadily become my favourite New Order album. When I came across this copy (Factory, 1983), it was in pristine condition, but it now bears witness to my (mostly careful) use. There's now a scratch somewhere towards the end of the first track Age of Consent which causes my turntable to loop. By some good fortune the looping point is perfectly aligned to a bar. I don't always notice it straight away. This record rarely makes it back down from the turntable to where it's supposed to live.

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I don't generally write consumer reviews, here or elsewhere; but I have been so impressed by this one I wanted to mention it.

For Holly's birthday this year, taking place under Lockdown, we decided to buy a year's subscription to "Disney+". Our current TV receiver (A Humax Freesat box) doesn't support it so I needed to find some other way to get it onto the TV.

After a short bit of research, I bought the "Roku Express" streaming media player. This is the most basic streamer that Roku make, bottom of their range. For a little bit more money you can get a model which supports 4K (although my TV obviously doesn't: it, and the basic Roku, top out at 1080p) and a bit more gets you a "stick" form-factor and a Bluetooth remote (rather than line-of-sight IR).

I paid £20 for the most basic model and it Just Works. The receiver is very small but sits comfortably next to my satellite receiver-box. I don't have any issues with line-of-sight for the IR remote (and I rely on a regular IR remote for the TV itself of course). It supports Disney+, but also all the other big name services, some of which we already use (Netflix, YouTube BBC iPlayer) and some of which we didn't, since it was too awkward to access them (Google Play, Amazon Prime Video). It has now largely displaced the FreeSat box for accessing streaming content because it works so well and everything is in one place.

There's a phone App that remote-controls the box and works even better than the physical remote: it can offer a full phone-keyboard at times when you need to input text, and can mute the TV audio and put it out through headphones attached to the phone if you want.

My aging Plasma TV suffers from burn-in from static pictures. If left paused for a duration the Roku goes to a screensaver that keeps the whole frame moving. The FreeSat doesn't do this. My Blu Ray player does, but (I think) it retains some static elements.

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Older posts are available on the all posts page.


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