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* 5001 - drop the :(scenario) DSLKartik Agaram2019-03-121-181/+241
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I've been saying for a while[1][2][3] that adding extra abstractions makes things harder for newcomers, and adding new notations doubly so. And then I notice this DSL in my own backyard. Makes me feel like a hypocrite. [1] https://news.ycombinator.com/item?id=13565743#13570092 [2] https://lobste.rs/s/to8wpr/configuration_files_are_canary_warning [3] https://lobste.rs/s/mdmcdi/little_languages_by_jon_bentley_1986#c_3miuf2 The implementation of the DSL was also highly hacky: a) It was happening in the tangle/ tool, but was utterly unrelated to tangling layers. b) There were several persnickety constraints on the different kinds of lines and the specific order they were expected in. I kept finding bugs where the translator would silently do the wrong thing. Or the error messages sucked, and readers may be stuck looking at the generated code to figure out what happened. Fixing error messages would require a lot more code, which is one of my arguments against DSLs in the first place: they may be easy to implement, but they're hard to design to go with the grain of the underlying platform. They require lots of iteration. Is that effort worth prioritizing in this project? On the other hand, the DSL did make at least some readers' life easier, the ones who weren't immediately put off by having to learn a strange syntax. There were fewer quotes to parse, fewer backslash escapes. Anyway, since there are also people who dislike having to put up with strange syntaxes, we'll call that consideration a wash and tear this DSL out. --- This commit was sheer drudgery. Hopefully it won't need to be redone with a new DSL because I grow sick of backslashes.
* 4987 - support `browse_trace` tool in SubXKartik Agaram2019-02-251-1/+1
| | | | | | | | | | | | | | | | | | I've extracted it into a separate binary, independent of my Mu prototype. I also cleaned up my tracing layer to be a little nicer. Major improvements: - Realized that incremental tracing really ought to be the default. And to minimize printing traces to screen. - Finally figured out how to combine layers and call stack frames in a single dimension of depth. The answer: optimize for the experience of `browse_trace`. Instructions occupy a range of depths based on their call stack frame, and minor details of an instruction lie one level deeper in each case. Other than that, I spent some time adjusting levels everywhere to make `browse_trace` useful.
* 4266 - space for alloc-id in heap allocationsKartik Agaram2018-06-241-6/+6
| | | | This has taken me almost 6 weeks :(
* 4262 - literal 'null'Kartik Agaram2018-06-171-1/+1
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* 4258 - undo 4257Kartik Agaram2018-06-151-6/+6
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* 4257 - abortive attempt at safe fat pointersKartik Agaram2018-06-151-6/+6
| | | | | | | | | | | | | | | | I've been working on this slowly over several weeks, but it's too hard to support 0 as the null value for addresses. I constantly have to add exceptions for scalar value corresponding to an address type (now occupying 2 locations). The final straw is the test for 'reload': x:num <- reload text 'reload' returns an address. But there's no way to know that for arbitrary instructions. New plan: let's put this off for a bit and first create support for literals. Then use 'null' instead of '0' for addresses everywhere. Then it'll be easy to just change what 'null' means.
* 4179 - experiment: rip out memory reclamationKartik K. Agaram2018-01-031-19/+0
| | | | | | | | | | | | | | | | | | | | | I have a plan for a way to avoid use-after-free errors without all the overheads of maintaining refcounts. Has the nice side-effect of requiring manual memory management. The Mu way is to leak memory by default and build tools to help decide when and where to expend effort plugging memory leaks. Arguably programs should be distributed with summaries of their resource use characteristics. Eliminating refcount maintenance reduces time to run tests by 30% for `mu edit`: this commit parent mu test: 3.9s 4.5s mu test edit: 2:38 3:48 Open questions: - making reclamation easier; some sort of support for destructors - reclaiming local scopes (which are allocated on the heap) - should we support automatically reclaiming allocations inside them?
* 4106Kartik K. Agaram2017-11-031-1/+1
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* 4104Kartik K. Agaram2017-11-031-2/+2
| | | | | Stop hardcoding Max_depth everywhere; we had a default value for a reason but then we forgot all about it.
* 3877Kartik K. Agaram2017-05-261-2/+2
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* 3654Kartik K. Agaram2016-11-081-2/+2
| | | | | | | | Follow-up to commit 3321: move get_base_type() more thoroughly to layer 55. The notion of a base_type doesn't really make sense before we introduce type ingredients and shape-shifting containers, and it simplifies early layers a *lot* even including the cost of that *ugly* preamble in layer 55 to retrofit all the places.
* 3522Kartik K. Agaram2016-10-191-4/+4
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* 3481Kartik K. Agaram2016-10-081-2/+2
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* 3393Kartik K. Agaram2016-09-171-1/+1
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* 3390Kartik K. Agaram2016-09-171-2/+2
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* 3389Kartik K. Agaram2016-09-171-20/+20
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* 3385Kartik K. Agaram2016-09-171-88/+88
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* 3381Kartik K. Agaram2016-09-171-12/+12
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* 3379Kartik K. Agaram2016-09-171-7/+7
| | | | Can't use type abbreviations inside 'memory-should-contain'.
* 3377Kartik K. Agaram2016-09-171-5/+5
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* 3374Kartik K. Agaram2016-09-161-4/+4
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* 3309Kartik K. Agaram2016-09-091-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rip out everything to fix one failing unit test (commit 3290; type abbreviations). This commit does several things at once that I couldn't come up with a clean way to unpack: A. It moves to a new representation for type trees without changing the actual definition of the `type_tree` struct. B. It adds unit tests for our type metadata precomputation, so that errors there show up early and in a simpler setting rather than dying when we try to load Mu code. C. It fixes a bug, guarding against infinite loops when precomputing metadata for recursive shape-shifting containers. To do this it uses a dumb way of comparing type_trees, comparing their string representations instead. That is likely incredibly inefficient. Perhaps due to C, this commit has made Mu incredibly slow. Running all tests for the core and the edit/ app now takes 6.5 minutes rather than 3.5 minutes. == more notes and details I've been struggling for the past week now to back out of a bad design decision, a premature optimization from the early days: storing atoms directly in the 'value' slot of a cons cell rather than creating a special 'atom' cons cell and storing it on the 'left' slot. In other words, if a cons cell looks like this: o / | \ left val right ..then the type_tree (a b c) used to look like this (before this commit): o | \ a o | \ b o | \ c null ..rather than like this 'classic' approach to s-expressions which never mixes val and right (which is what we now have): o / \ o o | / \ a o o | / \ b o null | c The old approach made several operations more complicated, most recently the act of replacing a (possibly atom/leaf) sub-tree with another. That was the final straw that got me to realize the contortions I was going through to save a few type_tree nodes (cons cells). Switching to the new approach was hard partly because I've been using the old approach for so long and type_tree manipulations had pervaded everything. Another issue I ran into was the realization that my layers were not cleanly separated. Key parts of early layers (precomputing type metadata) existed purely for far later ones (shape-shifting types). Layers I got repeatedly stuck at: 1. the transform for precomputing type sizes (layer 30) 2. type-checks on merge instructions (layer 31) 3. the transform for precomputing address offsets in types (layer 36) 4. replace operations in supporting shape-shifting recipes (layer 55) After much thrashing I finally noticed that it wasn't the entirety of these layers that was giving me trouble, but just the type metadata precomputation, which had bugs that weren't manifesting until 30 layers later. Or, worse, when loading .mu files before any tests had had a chance to run. A common failure mode was running into types at run time that I hadn't precomputed metadata for at transform time. Digging into these bugs got me to realize that what I had before wasn't really very good, but a half-assed heuristic approach that did a whole lot of extra work precomputing metadata for utterly meaningless types like `((address number) 3)` which just happened to be part of a larger type like `(array (address number) 3)`. So, I redid it all. I switched the representation of types (because the old representation made unit tests difficult to retrofit) and added unit tests to the metadata precomputation. I also made layer 30 only do the minimal metadata precomputation it needs for the concepts introduced until then. In the process, I also made the precomputation more correct than before, and added hooks in the right place so that I could augment the logic when I introduced shape-shifting containers. == lessons learned There's several levels of hygiene when it comes to layers: 1. Every layer introduces precisely what it needs and in the simplest way possible. If I was building an app until just that layer, nothing would seem over-engineered. 2. Some layers are fore-shadowing features in future layers. Sometimes this is ok. For example, layer 10 foreshadows containers and arrays and so on without actually supporting them. That is a net win because it lets me lay out the core of Mu's data structures out in one place. But if the fore-shadowing gets too complex things get nasty. Not least because it can be hard to write unit tests for features before you provide the plumbing to visualize and manipulate them. 3. A layer is introducing features that are tested only in later layers. 4. A layer is introducing features with tests that are invalidated in later layers. (This I knew from early on to be an obviously horrendous idea.) Summary: avoid Level 2 (foreshadowing layers) as much as possible. Tolerate it indefinitely for small things where the code stays simple over time, but become strict again when things start to get more complex. Level 3 is mostly a net lose, but sometimes it can be expedient (a real case of the usually grossly over-applied term "technical debt"), and it's better than the conventional baseline of no layers and no scenarios. Just clean it up as soon as possible. Definitely avoid layer 4 at any time. == minor lessons Avoid unit tests for trivial things, write scenarios in context as much as possible. But within those margins unit tests are fine. Just introduce them before any scenarios (commit 3297). Reorganizing layers can be easy. Just merge layers for starters! Punt on resplitting them in some new way until you've gotten them to work. This is the wisdom of Refactoring: small steps. What made it hard was not wanting to merge *everything* between layer 30 and 55. The eventual insight was realizing I just need to move those two full-strength transforms and nothing else.
* 3209Kartik K. Agaram2016-08-171-2/+2
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* 3154 - reorg before making 'random' more testableKartik K. Agaram2016-07-271-0/+381