Inline a function by patching a few variable names. I don't even have to
worry about `return` statements if there's a single call and it's in tail
position in the caller.
We don't have support for browsing them yet. Just errors for now, which
should only be a line or two. Larger traces might be useful for inspecting
results of macroexpansion.
It turns out there's another problem, and it predates the ability to create
new definitions:
ctrl-s triggers a call to `evaluate`, which inserts a new definition
into globals. which has a null gap buffer.
All this happens long before the new code in this commit, resulting in a
null gap buffer by the time we get to word-at-cursor.
Which in turn happens because we perform a raw `evaluate`, which doesn't
update the gap buffer like `run` does (using `maybe-stash-gap-buffer-to-global`).
And arguably `evaluate` shouldn't mess with the gap buffer. Gap buffers
are a UI concern.
The hardest version of this immediate scenario: It's unclear how to guarantee
that every definition have a gap buffer, when two definitions may share
one (closures sharing a lexical environment).
New plan:
- improve the logic for detecting definitions. Looking at the outermost
layer isn't enough. And a single expression can create multiple definitions.
- extract a helper to attach a single gap buffer to multiple definitions.
- have the UI detect conflicts in gap buffers and prompt the user for
a decision if a different gap buffer already exists for a definition.
I wrote a comment about how some code was not covered by tests, and then
promptly forgot what it was for. This is why we need tests.
Now the hack is gone.
It turns out (bowboard screen 128) on a real screen massively slowed down
and ran out of memory since commit e2ab1b30b1 on May 19. The culprit was
these changes, which created memory allocations for a new trace on every
recursive call.
I originally had some vague desire to isolate these calls from the user-visible
trace. That's expensive enough that I'll wait until it becomes a concern
before trying to isolate again.
It turns out I have a problem with trace depth somewhere which I just wasn't
noticing before. Running certain sandboxes (line; maybe loops?) twice was
causing traces to no longer start at depth 1, which implies that they weren't
terminating at depth 1. This became a lot more obvious since I instituted
a max-depth.
This was quite difficult to diagnose. The issue I noticed was that brline
had stopped working. All the bugs in previous commits were hiding the cause.
Once I cleaned them up, I realized the problem was that the `(,x0 ,y0)
was triggering the nested-backquote check. The fix was fairly straightforward
then (even though I didn't yet understand why). But how to write a test
for this? I spent some time trying to do so without defining a macro using
literal macros, before I realized:
You can't call literal macros; we don't have first-class macros.
Trying to insert literal macro support just breaks everything because we
have no way to distinguish between a literal macro call and the stage in
macroexpand where a symbol has been replaced with its macro definition.
How do you explain stuff like this? I grow weary of Lisp.
There's still some issue in loading the entire definition of brline from
data.limg.
Now that we never have a null trace, tracing errors is always safe. And
now that we're running with low trace max-depth we're more likely to run
into problems with missing errors in the trace.
I was aware of some complications. The various indexes and y coordinates
in the trace's cache would be unstable and need to be recomputed. But it's
surprising that the trace _completely disappears_.
The goal: the sandbox initially maintains a shallow trace. As you expand
into the trace, the environment reruns the sandbox at greater depth as
needed.
The challenge: expanding happens within edit-trace, which doesn't have
the whole sandbox needed to re-run the sandbox. We'll either need to expand
the trace's capabilities to include the whole sandbox, or duplicate some
logic to decide when to run the sandbox.
So far we were only doing so for the first few lines, just enough to render
one page's worth of lines. We'd have probably noticed if we collapsed some
lines after re-evaluating.
I've been stymied for a week wondering how to reliably compute trace-line
identity. A trace can have multiple identical lines. Only some of them
may be visible at any point. How to remember which is which across re-evaluations?
There's no easy answer. I'm just going to keep things ad hoc. When you
re-evaluate, new lines can currently pop into visibility. However we guarantee
that just moving around the trace will be stable, thanks to the visible
bit being cached within each trace-line. Scrolling will be similar. Reevaluating
may cause the trace to be perturbed up or down. However, just scrolling
around will work reliably.
We now use traces everywhere for error-checking. Null traces introduce
the possibility of changing a functions error response, and therefore its
semantics.
Another commit, another bugfix.
Some snippets from my currently exploding todo list:
- always investigate lookup errors immediately. Beyond the root cause, they should never happen at the moment, while we aren't reclaiming memory.
we should always return a more precise error message. Usually involving null pointer checks.
- on abort, print out stack trace
- emit mapping of labels to addresses during survey
- store a mapping of symbols somewhere in the code image
- stop allocating 1KB per token; expand space for tokens as needed
In the process I spent a long time tracking down a stray TODO in 108write.subx
that I thought would abort but didn't since the switch to baremetal.
Then after I reintroduced that assertion I had to go track down a bunch
of buffer sizes. Stream sizes continue to be a huge mess.
Current plan:
- some way to define macros. For now:
(def f (litmac litfn () (a b) `(+ ,a , b)))
- macroexpand will expand calls by passing them through the cdr
(f 3 4)
macroexpand: ((litfn () (a b) `(+ ,a ,b)) 3 4)
=> (+ 3 4)
eval: (+ 3 4) => 7
