Merge remote-tracking branch 'origin/main' into spec-split

# Conflicts:
#	src/api/run.rkt
#	src/syntax/platform.rkt
#	src/syntax/read.rkt

Author: pavpanchekha

AGENTS.md

@@ -1,4 +1,21 @@
 
+# Structure
+
+- `src/core` has key algorithms and `src/syntax` key concepts; these
+  are the most critical and highest value parts of the project. Should
+  be fast and effective, complex algorithms could well be worth it.
+- `src/core/explain.rkt` and `src/core/localize.rkt` are sorta-kinda
+  deprecated. Keep them working, but can get slower or worse.
+- The rest of `src` is, conceptually, glue code. Simple is best,
+  optimize for maintainability. All of `src` goes through human code
+  review and should match surrounding style.
+- Modules layer `utils < syntax < core < reports < api`. Lower layers
+  do not import higher layers.
+- `infra/` is for development only. Some code in there is abandon-ware
+  of AI-written and unreviewed. Don't reference for code style and not
+  all features in there are actually used. Changing users often easier
+  than code heroics.
+
 # Formatting
 
 - Use `map` over `for/list` only if it avoids a `lambda`.
@@ -7,45 +24,43 @@
 - Do not code defensively. Do not do runtime type checks or fallback.
   Prefer to examine all callers to establish types, or if they can
   differ prefer `match` with explicit patterns for all cases, to
-  ensure that an unanticipated values at any point cause errors.
+  ensure that unanticipated value cause explicit errors.
 - Format Racket code with `make fmt` at the top level.
 - Check `git diff` and delete dead code before finishing a task.
 - Update docs in `www/doc/2.3/` if you change user-visible options.
-- Enforce module layering `utils < syntax < core < reports < api`: do not add imports from a lower layer to a higher layer.
 
 # Testing
 
 - If you change the Herbie core, test that your changes work with
   `racket src/main.rkt report bench/tutorial.fpcore tmp`. This should
   take about 5-10 seconds and all of the tests should pass with
   perfect accuracy. You can also use other benchmark suites if asked.
-- If you need to store two reports name the folders `tmp-X` for some X.
 - Arguments come after the word `report` before any other arguments.
-- Herbie prints a seed every time it runs; you can pass `--seed N`
-  after the "report" argument to fix the seed reproducibly.
-- You can pass `--timeout T` to time out a benchmark after T seconds.
-- After running tests, `tmp` will have one directory per benchmark.
+- Herbie prints a seed every time it runs; pass `--seed N` for
+  reproducibility.
+- Pass `--timeout T` to time out a benchmark after T seconds.
   Each has a detailed `graph.html`, including tracebacks for crashes.
+- After running tests, `tmp` will have one directory per benchmark.
+- For multiple reports name the folders `tmp-<whatever>`.
 - The default e-graph backend is `egg`; pass `--enable generate:egglog`
-  to enable the `egglog` backend. You may need to add `~/.cargo/bin`
-  to the `PATH`.
+  to enable the `egglog` backend.
 - Some files have unit tests; run them with `raco test <file>`.
 
 # Observability
 
-- `jq` is installed, use it
 - If you're investigating a single benchmark, copy it to a file named
   `test.fpcore` and run just that file.
 - Herbie runs output a `tmp/<benchmark>/timeline.json` with rich
   observability data for each benchmark.
-- A timeline is a list of phases, each a map from key to "table",
+- This timeline is a list of phases, each a map from key to "table",
   each table is a list of fixed-length arrays.
 - Timeline types are defined in `src/utils/timeline.rkt`; HTML
   generation is defined in `src/reports/timeline.rkt`.
 - Add to the timeline with `(timeline-push! 'type val1 val2 ...)`. The
   `val`s must be JSON-compatible, so convert symbols to strings.
-- Herbie runs generates a profile in `tmp/<benchmark>/profile.json`.
+- Herbie runs generate a profile in `tmp/<benchmark>/profile.json`.
 - You can also dump GC/memory data to `dump-trace.json` with `--enable
   dump:trace`, Rival commands with `--enable dump:rival`, and egglog
   commands with `--enable dump:egglog`. Dumps go in `dump-XXX` in the
-  current directory. Clean that directory when done.
+  current directory. New runs *add files* to those directories, so
+  clean up when done.

bench/hamming/series.fpcore

@@ -57,6 +57,10 @@
  :alt 
  (! :herbie-platform c
   (+ (/ 1 a) (/ 1 b)))
+ :alt
+ (! :herbie-platform c
+  (+ eps (+ (/ (if (== (* a eps) 0) 1 (/ (* eps a) (expm1 (* eps a)))) a)
+            (/ (if (== (* b eps) 0) 1 (/ (* eps b) (expm1 (* eps b)))) b))))
 
  (/
   (* eps (- (exp (* (+ a b) eps)) 1))