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* 3663 - fix a refcounting bug: '(type)' != 'type'Kartik K. Agaram2016-11-101-2/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This was a large commit, and most of it is a follow-up to commit 3309, undoing what is probably the final ill-considered optimization I added to s-expressions in Mu: I was always representing (a b c) as (a b . c), etc. That is now gone. Why did I need to take it out? The key problem was the error silently ignored in layer 30. That was causing size_of("(type)") to silently return garbage rather than loudly complain (assuming 'type' was a simple type). But to take it out I had to modify types_strictly_match (layer 21) to actually strictly match and not just do a prefix match. In the process of removing the prefix match, I had to make extracting recipe types from recipe headers more robust. So far it only matched the first element of each ingredient's type; these matched: (recipe address:number -> address:number) (recipe address -> address) I didn't notice because the dotted notation optimization was actually representing this as: (recipe address:number -> address number) --- One final little thing in this commit: I added an alias for 'assert' called 'assert_for_now', to indicate that I'm not sure something's really an invariant, that it might be triggered by (invalid) user programs, and so require more thought on error handling down the road. But this may well be an ill-posed distinction. It may be overwhelmingly uneconomic to continually distinguish between model invariants and error states for input. I'm starting to grow sympathetic to Google Analytics's recent approach of just banning assertions altogether. We'll see..
* 3662Kartik K. Agaram2016-11-101-2/+2
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* 3656Kartik K. Agaram2016-11-101-1/+1
| | | | | | | | | | | | | | Periodic cleanup to replace 'reply' with 'return' everywhere in the repo. I use 'reply' for students to help reinforce the metaphor of function calls as being like messages through a pipe. But that causes 'reply' to get into my muscle memory when writing Mu code for myself, and I worry that that makes Mu seem unnecessarily alien to anybody reading on Github. Perhaps I should just give it up? I'll try using 'return' with my next student.
* 3654Kartik K. Agaram2016-11-081-10/+28
| | | | | | | | 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.
* 3653Kartik K. Agaram2016-11-081-0/+7
| | | | | | | | | Don't crash on bad types. I need to be more careful in distinguishing between the two causes of constraint violations: bad input and internal bugs. Maybe I should create a second assert() to indicate "this shouldn't really be an assert, but I'm too lazy to think about it right now."
* 3643Kartik K. Agaram2016-11-071-2/+2
| | | | | Standardize on calling literate waypoints "Special-cases" rather than "Cases". Invariably there's a default path already present.
* 3640Kartik K. Agaram2016-11-061-10/+7
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* 3638Kartik K. Agaram2016-11-061-16/+15
| | | | Reorder a couple of nonsensically-placed fragments.
* 3637 - better 'missing type ingredient' errorsKartik K. Agaram2016-11-061-21/+21
| | | | | | | | | | | | Programming languages need some higher-level language construct that's neither an interface nor a class nor an object but a *collection of mutually recursive functions with a well-defined set of entry points and common ingredients. Perhaps the solution here is the Haskell "save your boilerplate" paper. For now I'm going to include the purpose in auxiliary variable names that aren't really necessary for the core processing of a function. Thanks Caleb Couch for reporting this issue.
* 3522Kartik K. Agaram2016-10-191-2/+2
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* 3390Kartik K. Agaram2016-09-171-2/+2
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* 3389Kartik K. Agaram2016-09-171-7/+7
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* 3385Kartik K. Agaram2016-09-171-43/+43
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* 3381Kartik K. Agaram2016-09-171-2/+2
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* 3379Kartik K. Agaram2016-09-171-1/+1
| | | | Can't use type abbreviations inside 'memory-should-contain'.
* 3376 - start maximally using all type abbreviationsKartik K. Agaram2016-09-171-8/+8
| | | | | | It might be too much, particularly if students start peeking inside .mu files early. But worth a shot for not just to iron out the kinks in the abbreviation system.
* 3327Kartik K. Agaram2016-09-111-2/+2
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* 3321Kartik K. Agaram2016-09-101-0/+11
| | | | | | | | | | | Clean up another case (after commit 3309) of premature support for shape-shifting recipes, where early layers had code without corresponding tests. One addendum to commit 3309: the proximal cause for triggering the rewrite of type_trees was that I realized to_string() and variants were lying to me while debugging; they couldn't distinguish between `(a . b)` and `((a) . b)`
* 3309Kartik K. Agaram2016-09-091-47/+156
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* 3308Kartik K. Agaram2016-09-091-55/+11
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* 3298Kartik K. Agaram2016-09-051-15/+0
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* 3297 - run unit tests before scenariosKartik K. Agaram2016-09-051-0/+17
| | | | | | | | | | | | | | I've been putting up for some time with the tension between wanting to show scenarios at the top of the layer even if I want to *run* any unit tests of sub-components introduced within the layer before them. Turned out to be an easy fix. We don't have very many of these, and the unit tests in the early layers don't compete with any scenarios, so I don't need to mess with them. But this is a key tool in my toolkit, to be able to decouple presentation order from run order for tests. Though now the separate compilation units are again unbalanced; sigh.
* 3294Kartik K. Agaram2016-09-021-1/+1
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* 3286Kartik K. Agaram2016-08-311-20/+0
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* 3273Kartik K. Agaram2016-08-281-2/+2
| | | | | | | | | | | Undo 3272. The trouble with creating a new section for constants is that there's no good place to order it since constants can be initialized using globals as well as vice versa. And I don't want to add constraints disallowing either side. Instead, a new plan: always declare constants in the Globals section using 'extern const' rather than just 'const', since otherwise constants implicitly have internal linkage (http://stackoverflow.com/questions/14894698/why-does-extern-const-int-n-not-work-as-expected)
* 3272Kartik K. Agaram2016-08-281-1/+1
| | | | | | Move global constants into their own section since we seem to be having trouble linking in 'extern const' variables when manually cleaving mu.cc into separate compilation units.
* 3212 - bugfix in refcount managementKartik K. Agaram2016-08-171-1/+6
| | | | | | | | | | | When updating refcounts for a typed segment of memory being copied over with another, we were only ever using the new copy's data to determine any tags for exclusive containers. Looks like the right way to do refcounts is to increment and decrement separately. Hopefully this is a complete fix for the intermittent but non-deterministic errors we've been encountering while running the edit/ app.
* 3104Kartik K. Agaram2016-07-061-3/+18
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* 3060Kartik K. Agaram2016-06-171-1/+1
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* 3043Kartik K. Agaram2016-06-101-1/+1
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* 3010Kartik K. Agaram2016-05-251-2/+2
| | | | | | | | | | insert_container is getting pretty gnarly. It's spread across two layers (containers and shape-shifting containers), and since it has to deal with extending existing containers it's coiled in on itself, constantly reading and writing the Type table. Maybe I should uncoil the case of extending a container and make it separate from defining a new container.
* 2990Kartik K. Agaram2016-05-201-2/+2
| | | | | | | | | | Standardize quotes around reagents in error messages. I'm still sure there's issues. For example, the messages when type-checking 'copy'. I'm not putting quotes around them because in layer 60 I end up creating dilated reagents, and then it's a bit much to have quotes and (two kinds of) brackets. But I'm sure I'm doing that somewhere..
* 2987Kartik K. Agaram2016-05-201-0/+612