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* 3707Kartik K. Agaram2016-12-121-5/+2
| | | | | | | | | | | | | | | | | | Be more disciplined about tagging 2 different concepts in the codebase: a) Use the phrase "later layers" to highlight places where a layer doesn't have the simplest possible self-contained implementation. b) Use the word "hook" to point out functions that exist purely to provide waypoints for extension by future layers. Since both these only make sense in the pre-tangled representation of the codebase, using '//:' and '#:' comments to get them stripped out of tangled output. (Though '#:' comments still make it to tangled output at the moment. Let's see if we use it enough to be worth supporting. Scenarios are pretty unreadable in tangled output anyway.)
* 3663 - fix a refcounting bug: '(type)' != 'type'Kartik K. Agaram2016-11-101-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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..
* 3659Kartik K. Agaram2016-11-101-1/+1
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* 3656Kartik K. Agaram2016-11-101-3/+3
| | | | | | | | | | | | | | 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.
* 3643Kartik K. Agaram2016-11-071-4/+4
| | | | | Standardize on calling literate waypoints "Special-cases" rather than "Cases". Invariably there's a default path already present.
* 3561Kartik K. Agaram2016-10-221-3/+3
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* 3522Kartik K. Agaram2016-10-191-4/+4
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* 3394Kartik K. Agaram2016-09-171-9/+15
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* 3393Kartik K. Agaram2016-09-171-5/+5
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* 3390Kartik K. Agaram2016-09-171-16/+16
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* 3389Kartik K. Agaram2016-09-171-31/+31
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* 3381Kartik K. Agaram2016-09-171-1/+1
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* 3380Kartik K. Agaram2016-09-171-40/+40
| | | | | One more place we were missing expanding type abbreviations: inside container definitions.
* 3376 - start maximally using all type abbreviationsKartik K. Agaram2016-09-171-2/+2
| | | | | | 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.
* 3309Kartik K. Agaram2016-09-091-9/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* 3260Kartik K. Agaram2016-08-261-1/+1
| | | | | array length = number of elements array size = in locations
* 3255Kartik K. Agaram2016-08-261-8/+9
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* 3215Kartik K. Agaram2016-08-171-3/+3
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* 3214Kartik K. Agaram2016-08-171-1/+1
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* 3213Kartik K. Agaram2016-08-171-2/+1
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* 3202 - bugfix: 'start-running' and refcountsKartik K. Agaram2016-08-161-2/+2
| | | | | | | | | | | | | | | | | | | | | | When you pass an ingredient to a recipe using 'start-running' it mostly behaves identically to performing a regular function call. However, if the calling function completed before the new routine had a chance to run, the ingredients passed in ran the risk of being reclaimed. In response, let's always increment refcounts at the time of a function call rather than when the ingredients are read inside the callee. Now the summary of commit 3197 is modified to this: Update refcounts of products after every instruction, EXCEPT: a) when instruction is a non-primitive and the callee starts with 'local-scope' (because it's already not decremented in 'return') OR: b) when instruction is primitive 'next-ingredient' or 'next-ingredient-without-typechecking'
* 3199Kartik K. Agaram2016-08-161-6/+7
| | | | | | | | | Never mind, just close your nose and replace that function parameter with a global variable. This may not always be the solution for the problem of layers being unable to add parameters and arguments, but here it works well and it's unclear what problems the global might cause.
* 3198Kartik K. Agaram2016-08-161-15/+16
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* 3197Kartik K. Agaram2016-08-161-5/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace an integer with a boolean across two layers of function calls. It has long been one of the ugliest consequences of my approach with layers that functions might need to be introduced with unnecessary arguments simply because we have no clean way to add parameters to a function definition after the fact -- or to add the default argument corresponding to that parameter in calls. This problem is exacerbated by the redundant argument having to be passed in through multiple layers of functions. In this instance: In layer 20 we define write_memory with an argument called 'saving_instruction_products' which isn't used yet. In layer 36 we reveal that we use this argument in a call to should_update_refcounts_in_write_memory() -- where it is again not used yet. Layer 43 finally clarifies what we're shooting for: a) In general when we need to update some memory, we always want to update refcounts. b) The only exception is when we're reclaiming locals in a function that set up its stack frame using 'local-scope' (signalling that it wants immediate reclamation). At that point we avoid decrementing refcounts of 'escaping' addresses that are being returned, and we also avoid incrementing refcounts of products in the caller instruction. The latter case is basically why we need this boolean and its dance across 3 layers. In summary, write_memory() needs to update refcounts except if: we're writing products for an instruction, the instruction is not a primitive, and the (callee) recipe for the instruction starts with 'local-scope'.
* 3196Kartik K. Agaram2016-08-161-1/+1
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* 2990Kartik K. Agaram2016-05-201-3/+3
| | | | | | | | | | 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..
* 2974Kartik K. Agaram2016-05-181-23/+4
| | | | Fix CI failure.
* 2973 - reclaim refcounts for local scopes againKartik K. Agaram2016-05-181-35/+147
| | | | | | More thorough redo of commit 2767 (Mar 12), which was undone in commit 2810 (Mar 24). It's been a long slog. Next step: write a bunch of mu code in the edit/ app in search of bugs.
* 2972 - abandon recursive containersKartik K. Agaram2016-05-171-0/+1
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* 2932Kartik K. Agaram2016-05-061-4/+4
| | | | | | | More consistent labeling of waypoints. Use types only when you need to distinguish between function overloadings. Otherwise just use variable names unless it's truly not apparent what they are (like that the result is a recipe in "End Rewrite Instruction").
* 2931 - be explicit about making copiesKartik K. Agaram2016-05-061-33/+33
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* 2864 - replace all address:shared with just addressKartik K. Agaram2016-04-241-34/+32
| | | | | | | Now that we no longer have non-shared addresses, we can just always track refcounts for all addresses. Phew!
* 2847Kartik K. Agaram2016-04-201-4/+4
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* 2846Kartik K. Agaram2016-04-201-5/+5
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* 2810 - undo 2767, reclaiming local allocationsKartik K. Agaram2016-03-241-20/+25
| | | | | | | | | | | | | | | | | | | | | | | I realize that there's still a serious problem with refcounts. Everything's fine as long as I copy those shared addresses manually elsewhere, but there's a couple of places where I just do a memcopy right now without any extra smarts: in 'copy' and 'merge' instructions. I need to replace support for arbitrary types in these instructions, and replace it with transforms to generate the right code. Mu basically needs copy constructors and destructors, so that containers can decrement the refcounts of any elements (or elements of elements, or elements of elements of elements..) that are shared addresses. But my confidence in this whole approach is shaken. Maybe I should stop this project. It's turning into a language+OS design project where I was hoping that being a toy would shelter me from these concerns. I just want to explore turning manual tests into reproducible automatic ones. Maybe I should just build libraries for each interface to hardware (network, disk, screen, keyboard, ...) in C++11 or something. Use no high-level libraries for sockets, files, etc. Instead rely on just the kernel syscalls, memory allocator, RAII, STL. Build things from scratch atop those building blocks.
* 2803Kartik K. Agaram2016-03-211-2/+2
| | | | | Show more thorough information about instructions in the trace, but keep the original form in error messages.
* 2773 - switch to 'int'Kartik K. Agaram2016-03-131-8/+8
| | | | This should eradicate the issue of 2771.
* 2767 - reclaim refcounts for local variablesKartik K. Agaram2016-03-121-0/+34
| | | | | | This uncovered a second bug (besides 2766) -- I was manually doing the work of 'new-fake-console' inside 'assume-console' but forgetting to increment a refcount.
* 2764Kartik K. Agaram2016-03-121-2/+3
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* 2762Kartik K. Agaram2016-03-121-2/+2
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* 2735 - define recipes using 'def'Kartik K. Agaram2016-03-081-10/+10
| | | | | | | | | | | | I'm dropping all mention of 'recipe' terminology from the Readme. That way I hope to avoid further bike-shedding discussions while I very slowly decide on the right terminology with my students. I could be smarter in my error messages and use 'recipe' when code uses it and 'function' otherwise. But what about other words like ingredient? It would all add complexity that I'm not yet sure is worthwhile. But I do want separate experiences for veteran programmers reading about Mu on github and for people learning programming using Mu.
* 2728 - don't ignore /space: while checking typesKartik K. Agaram2016-03-041-0/+15
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* 2718 - stop crashing on unknown spaceKartik K. Agaram2016-02-261-0/+1
| | | | | I'm going to stop wasting precious first-line characters on 'bugfix:'. It's going to be all bugfixes for a while I think.
* 2712Kartik K. Agaram2016-02-261-8/+8
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* 2707Kartik K. Agaram2016-02-251-4/+1
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* 2703Kartik K. Agaram2016-02-251-5/+5
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* 2701 - turn some warnings into errorsKartik K. Agaram2016-02-251-1/+1
| | | | | | | I really have only one warning left: when somebody redefines a function. I think I'm going to just turn that into an error as well and drop the notion of warnings altogether. Anytime we find something wrong we stop running the program. This is a place where hygiene is justified.
* 2680Kartik K. Agaram2016-02-201-1/+1
| | | | Delete all the [] that has crept in since 2377 in November.
* 2685Kartik K. Agaram2016-02-191-2/+2
| | | | | | | | | | | | | | | | Stack of plans for cleaning up replace_type_ingredients() and a couple of other things, from main problem to subproblems: include type names in the type_tree rather than in the separate properties vector make type_tree and string_tree real cons cells, with separate leaf nodes redo the vocabulary for dumping various objects: do we really need to_string and debug_string? can we have a version with *all* information? can we have to_string not call debug_string? This commit nibbles at the edges of the final task, switching from member method syntax to global function like almost everything else. I'm mostly using methods just for STL in this project.
* 2645Kartik K. Agaram2016-02-101-1/+1
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