The mechanical half, ahead of the parser change that needs it. tools/unit-return.py
fills the empty slot with () and rewrites Unit as () wherever a type is spelled --
(Fn [i32] Unit), (Map i32 Unit), a return type written out.
Deciding whether a defn already had a return type is the whole difficulty, and
the script does it the way parse.ml did: is_type_form is transcribed rather than
improved, because being identical to the parser it replaces is what makes the
sweep meaning-preserving. It is re-runnable, so the lanes that branched before
this can have the same pass at merge:
python3 tools/unit-return.py .
python3 tools/unit-return.py --in-strings test/test_flan.ml test/test_acceptance.ml \
test/test_session.ml emacs/test-flan-dev.el emacs/test-flan-mode.el
python3 tools/unit-return.py --raw-ml lib/prelude.ml
python3 tools/unit-return.py --in-html web/index.html
-v logs every defn it saw and what it decided, which is how a sweep of 440 sites
gets reviewed at all. Embedded modes pool a file's type declarations across all
its fragments, because a snippet split across concatenation -- decls ^ "(defn f
[s [u8]] Cursor ...)" -- cannot see the names the other half declared; pooled
names count only in bare-symbol position, for the same reason the prelude's do.
A fragment that cuts off mid-form is skipped rather than guessed at. Five sites
in test_flan.ml still needed a hand, and they are in this commit.
Two things ride along because the sweep needs them: parse.ml reads a lone () as
the return type of a function with no body, which was not a shape the old
optional slot could produce; and the map refusals name () rather than Unit, since
that is now the spelling a caller wrote.
print-str, print-i64, print-f64, print-bytes, print-line and newline leave
the prelude. print and println are the whole printing surface now, and print
is the better call at every one of the sites that used them: it is the same
structural walk without the newline, so the no-newline case the family was
kept for is covered, and it takes the value as it is. The old print-i64
forced an explicit (i64 x) at every call site, because this language widens
nothing implicitly; that cast is gone from 127 places.
Dropping it moves one answer. hash-grid returns u64, and the cast through
the signed printer showed sand-headless's hash as -2851001042534928384.
print routes a u64 through flan_u64_to_bytes, so it now prints
15595743031174623232 — the same 64 bits, read as the unsigned number they
are. The pinned expectation follows the correction.
test-flan-dev.el and test_session.ml both reached for print-line as "a name
the prelude has"; they reach for rand-seed instead.
Finishing the text family the previous lane started. All three are over [u8]
and none of them allocates, which is what decides their shapes.
trim answers a slice of its input. That is the only shape available without an
allocator, and it is also the better one: there is no new storage, only a
narrower view of the caller's, so the result dies with its owner and trimming
modifies nothing. Both loops test (< lo hi), because an all-whitespace input
otherwise walks lo past hi and (slice s lo hi) traps on a reversed range - the
same trap the bounds table already asserts on. That input is in the case list.
index-of-bytes is naive and stays naive. Boyer-Moore wants a skip table sized
by the needle, which is an array, which is an allocation. The empty needle
answers Some 0 so that index-of-bytes and starts-with? agree on every needle,
and the length test returns before the loop so a needle longer than the
haystack cannot build a window off the end.
parse-f64 splits the work where the two halves actually differ: the grammar is
Flan's and the rounding is libc's. parse-i64 is entirely Flan because strtoll's
answers are wrong for a caller - 0 for "", 0 for "abc", 12 for "12x" - and not
because decimal-to-binary conversion is suspect. Reimplementing correctly
rounded conversion is a different and much larger problem than rejecting junk,
and IEEE-754 already guarantees strtod gives the same bits everywhere. So this
validates the whole slice and only a slice that is entirely a number reaches
bytes->f64. Every refusal in the table - "", "abc", "1x", ".", "1e", " 1",
"1 ", "0x10", "nan" - is a plausible number out of strtod.
Two caveats, both written into the source rather than discovered later. The
locale worry that keeps parse-i64 in Flan does apply to strtod's decimal point,
and is moot only because nothing in the runtime calls setlocale; if that stops
being true this is what breaks. And the length is capped at 511 because
flan_bytes_to_f64 truncates there - a validator that approved 600 digits would
be approving a different number than the one strtod reads.
digit? and space? exist because parse-f64 and trim need them, and calc-me loses
its own byte-identical digit?. One top-level namespace makes the second
definition an error rather than a shadow, which is the rule doing its job: two
copies that later drift apart is exactly what it prevents.
