An identifier's subscript list, a unary's operand and a binary's right-hand
side all lived in the same field the argument chain used, so ABS(-9),
MOD(A#, B# + 12) and any array reference in a parameter list were counted as
extra arguments and refused. Subscript lists move to .expr and arguments now
chain through a dedicated .next.
This is the third time the same collision was fixed; the first two moved it
along rather than removing it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
A host creating a variable while a script was suspended got it in whatever
scope was active -- usually a FOR or GOSUB body -- and it died when the body
popped, silently. Reaching for the root by hand returned NULL without raising,
because environment_get only auto-creates in the active environment.
Both are still true of environment_get, which is correct for what the
interpreter uses it for. The README and the example now point somewhere else.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The token has existed since the scanner was written and nothing read it, so
10 PRINT A$ : REM ... was a parse error. Leading separators are consumed
before each statement and an empty statement yields a NULL leaf rather than
an error, so a trailing colon and a run of them are both legal.
BASIC 7.0 scopes everything after THEN to the condition, which the reference
had no opinion about because it never got here. The rule is not "skip when
false": the rest of the line belongs to whichever arm was written last.
A whole FOR/NEXT on one line still does not loop -- block skipping works by
source line. Recorded in TODO.md as what group A has to fix first.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Chained subtraction and exponentiation fold left instead of abandoning the
rest of the line -- `1 - 2 - 3` gave -1 and dropped the `- 3`. A unary leaf's
operand moves to .left, so a negative literal is one argument again and a
second argument no longer overwrites it. An operator in a line's final column
survives. Hex literals reach the parser whole. A leading zero is padding, not
a radix.
Item 16 stays pinned: the fix works and costs an upstream golden case, which
is a decision rather than a defect.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The poll_key half of group E, against the akbasic_InputBackend record. The
libakgl implementation behind it is akgl_controller_poll_key(), which drains a
ring the library fills from SDL events the host pumps -- so the interpreter can
answer "is there a key waiting" without owning an event loop, which is what goal
3 requires.
GET and GETKEY differ in one way and it is the interesting one. GET takes
whatever is there including nothing, and an empty buffer is success with the
empty string rather than an error -- that is what happens on most iterations of
every GET loop ever written, and upstream is explicit that its poll reports it
the same way. GETKEY waits, and since the library may not block, waiting is
spelled as holding the step loop: the verb sets a flag and akbasic_runtime_step()
declines to advance until a key arrives. Every step still returns and a bounded
run() still comes back, so a host keeps its frame rate; the program simply does
not move past the GETKEY.
The PLAY queue is serviced before that check on purpose -- music should keep
playing while a program waits for a keypress. Withdrawing the input device while
a GETKEY is holding releases it rather than wedging the script on a device that
no longer exists.
Both verbs accept an integer variable as well as a string one and give it the raw
key code, which is what a program testing for cursor or function keys needs. No
key is code zero, matching what a C128 reports. A float variable is refused: it
is neither a character nor a code.
SCNCLR goes through the text sink rather than a device, because the sink is where
PRINT already goes and is the only thing that knows what a screen means for this
host. The stdio sink treats it as a no-op; clearing a pipe means nothing.
One thing worth knowing before writing any bounded-run test, and now commented in
tests/input_verbs.c: source lines are stored indexed by line number and the
cursor starts at zero, so a step is spent on each empty slot along the way. A
program at line 10 needs eleven steps before it has run anything.
70/70 ctest, clean under -Wall -Wextra, doxygen clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
SOUND, ENVELOPE, VOL, PLAY and TEMPO against the akbasic_AudioBackend record,
plus FILTER, which is in the table only so that it can be refused with a reason.
The PLAY note-string parser and TEMPO are here rather than in libakgl because
that is where its audio commit says they belong: a tone generator synthesises
pitches, but deciding that O4CDEFG is five quarter notes starting at middle C is
a language question.
PLAY does not block. On a C128 it holds the program until the last note ends,
which section 1.6 forbids outright, so it parses the string into a fixed queue
and returns; akbasic_runtime_step() releases one note at a time against whatever
time the host last passed to akbasic_runtime_settime(). The driver now steps one
at a time with the clock refreshed in between rather than making a single
unbounded run() call -- a tune whose notes all measured themselves against a
frozen zero would rush out at once. That loop is its own function because CATCH
expands to a break and PASS expands to a return of the context, and main()
returns an int; wrapping the loop is what the protocol prescribes for that shape.
src/audio_tables.c holds the three conversions, laid out as tables because each
is somewhere a wrong constant produces a plausible wrong pitch rather than an
error anybody would notice. Two are transcriptions -- the SID frequency formula
and its non-linear ADSR rate tables, where decay is exactly three times attack.
The third is not: BASIC 7.0 never published what a whole note lasts at a given
TEMPO, so 16000 ms at TEMPO 1 is a calibration choice putting a default quarter
note at 120 bpm, and it is labelled as a choice where it is made.
SOUND's frequency sweep is refused rather than faked, and filed upstream as
akgl_audio_sweep. The only way to fake it here is to re-issue tones from step(),
which ties audible pitch to how often the host calls us -- a tune that changes
key with the frame rate. FILTER is refused for the reason upstream already gave:
there is no filter stage and SDL3 has no primitive to build one from.
The PLAY parser is tested through akbasic_play_parse() directly rather than
through a program, because running one also runs the queue service -- and with
the clock at zero every duration has already expired, so the queue empties before
an assertion can look at it. Draining is correct behaviour and is tested on its
own; the parse tests ask a different question.
68/68 ctest, clean under -Wall -Wextra, doxygen clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
GRAPHIC, COLOR, DRAW, BOX, CIRCLE, PAINT, SCALE, SSHAPE, GSHAPE and LOCATE, all
against the akbasic_GraphicsBackend record rather than akgl_draw_* directly, so
src/runtime_graphics.c includes no SDL and the whole group is testable in a build
with no SDL on the machine.
The reference lists every one of these as unimplemented, so the semantics come
from Commodore BASIC 7.0 rather than from a port, and four places where a modern
renderer cannot do what a C128 did are recorded in TODO.md section 5 rather than
silently substituted:
- CIRCLE is drawn as a polygon of inc-degree segments and akgl_draw_circle is
deliberately unused. 7.0's CIRCLE takes two radii, an arc range and a rotation,
so the primitive could serve only the fully-defaulted call, and a shape that
changed character depending on whether the radii happened to be equal would be
worse than one uniformly a polygon.
- SSHAPE puts a SHAPE:<n> handle in the string variable rather than the pixels,
because a value's string is a fixed 256 bytes and a region is a device surface.
GSHAPE refuses a string without that prefix instead of parsing whatever digits
it finds and pasting an unrelated slot.
- BOX fills on a negative angle; 7.0 puts the fill flag after the rotation, which
would make a filled box a seventh argument.
- GRAPHIC stores its mode and honours only the one consequence that means
anything here -- mode 0 is text -- while still refusing an out-of-range mode,
since that is a typo worth catching.
PAINT surfaces the flood fill's AKERR_OUTOFBOUNDS as an error rather than
success. The device gives up when its span stack runs out having filled *part* of
the region, and a program that cannot tell that happened cannot recover from it.
Note the shape of that handler: HANDLE sets handled = true on the context, so a
FAIL_RETURN from inside the HANDLE block hands the caller something already
marked handled, whose FINISH_LOGIC then declines to pass it up and releases it --
the error disappears and PAINT reports success. Flag inside the block, raise
after FINISH.
COLOR, LOCATE and SCALE need no device on purpose, so a program can set itself up
before a host has lent it a renderer.
Adds a second golden corpus under tests/language/. The corpus in
deps/basicinterpret is a submodule and nothing here may add files to it, but
goal 2's new verbs still need the .bas/.txt half of their coverage. Registered
under local_ so a failure names which corpus it came from. What it can cover is
limited -- these verbs draw rather than print -- so the behaviour that reaches a
device is asserted against tests/mockdevice.h instead.
65/65 ctest, clean under -Wall -Wextra, doxygen clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Groups G, I and E are unblocked but cannot be written yet: the core library is
free of SDL and builds with no libakgl present, so a graphics verb cannot call
akgl_draw_* and a sound verb cannot call akgl_audio_*. This adds what they call
instead.
Three records of function pointers -- akbasic_GraphicsBackend, _AudioBackend and
_InputBackend -- in the same shape as akbasic_TextSink, and the same shape
libakgl uses for akgl_RenderBackend. akbasic_runtime_set_devices() attaches any
subset; all three may be NULL and that is the standalone driver's normal state,
so a runtime with no backends still comes up and still prints. A verb that needs
one it was not given raises the new AKBASIC_ERR_DEVICE rather than dereferencing
a NULL vtable.
Two decisions worth stating. The graphics record has no circle entry point:
BASIC 7.0's CIRCLE takes two radii, an arc range, a rotation and a degree
increment, which makes it a polygon by definition, so it will be built from line
calls rather than from akgl_draw_circle. And coordinates are double rather than
an integer pixel address, because SCALE makes them fractional and rounding at
each verb rather than once at the backend accumulates drift along a polyline.
akbasic_runtime_settime() is how SOUND, PLAY and TEMPO get a clock without the
library reading one. Section 1.6 forbids blocking or owning a loop, so the caller
that owns the frame owns the time -- which is what libakgl already does, since
akgl_actor_logic_changeframe takes curtimems as an argument. Left unset it is
zero and every duration expires immediately: audible, but never a hang.
AKBASIC_ERR_LAST is a sentinel rather than a status, so tests/error_codes.c walks
every code looking for an unnamed one without anybody remembering to widen the
loop when a code is added.
tests/mockdevice.h records every backend call as a formatted line. The graphics
and audio verbs emit nothing a golden file can compare, so that log is where
their assertions have to live -- and since it needs no SDL, the whole of groups
G, I and E stays testable in the default build.
62/62 ctest, clean under -Wall -Wextra, doxygen clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Carries the reference README across, adjusted where C changes the answer: cmake
instead of make, the ak* libraries instead of the go-sdl2 bindings, and the
limits table now includes the three ceilings the Go version did not need because
it called make().
The new "Embedding the interpreter" section is the point of the rewrite, so it
states the four rules the library holds to -- nothing terminates the process,
nothing calls malloc, no file-scope mutable state, the host owns the loop -- and
each was checked against the tree rather than asserted.
Adds akbasic_runtime_load(). Writing the section turned up a real gap: a host
usually already holds its script as a string and wants the sink reserved for
output, and the only path that existed was AKBASIC_MODE_RUNSTREAM reading the
program through the sink's readline, which forces a game to point its output
device at its source text. The alternative was reaching into the header's
"internal API" block for store_line. Neither is something to put in a README.
Adds examples/embed.c, which is the code the README quotes -- a custom sink, a
bounded per-frame run, and the PASS-not-CATCH rule for a loop inside an ATTEMPT.
It is built by every build and registered as a CTest case, so a signature change
breaks the build instead of rotting the document. The README's own snippet is
compiled separately as a check; both were run before committing.
The "What Isn't Implemented / Isn't Working" section leads with the eleven
inherited defects rather than burying them, because five of them were found by
this port and a reader deserves to know that 1 - 2 - 3 computes 1 - 2 before
they hit it. Corrected two claims while verifying: the runtime is 10.1MB rather
than the ~8MB first written, and its largest single cost is the environment pool
at 4.1MB, not the source table.
ctest 60/60; ASan+UBSan 60/60; no warnings under -Wall -Wextra.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Reproduces deps/basicinterpret in C, in the idiom of the ak* libraries. All 41
.bas files in the reference's corpus produce byte-identical stdout, including
the trailing double newline on an error line -- that comes from basicError
building a string ending in \n and handing it to Println, and
array_outofbounds.txt encodes it.
The corpus is driven in place from the submodule as 41 individual CTest cases
rather than copied, so it cannot drift from upstream. Eighteen unit tests cover
what the corpus cannot reach.
Three structural changes carry most of the work. Go's three reflection lookups
(Command*, Function*, ParseCommand*) become one sorted dispatch table in
src/verbs.c searched with bsearch; adding a verb is a row and two functions. The
five Go maps become one fixed open-addressed table over aksl_strhash_djb2. And
run(), which owned the process until MODE_QUIT, splits into step() plus a
bounded run() -- goal 3 requires a host game to be able to bound execution, and
nothing in the library now terminates the process or touches SDL.
Output goes through an akbasic_TextSink vtable. src/sink_stdio.c is what makes
the corpus runnable with no SDL present; the akgl-backed sink is still to come
and is blocked on libakgl having no text-measurement call.
src/convert.c exists because libakstdlib's aksl_ato* family cannot report a
conversion failure (its TODO.md 2.1.5). The reference checks strconv's error at
four sites and turns it into a BASIC error; routing those through aksl_atoi
would have turned four diagnosable errors into wrong answers, with VAL("garbage")
quietly returning 0. TODO.md 1.9 records which libakstdlib calls are cleared for
use here and which are not.
Reference defects are reproduced, not fixed: the golden files encode the observed
behaviour and a silent correction is a behaviour change. TODO.md section 6 lists
sixteen, and tests/known_reference_defects.c asserts the *correct* contract for
six of them under AKBASIC_KNOWN_FAILING_TESTS, so a fix shows up as
"unexpectedly passed". Five of the sixteen were found by this port and are new:
subtraction stops after one operator so 1-2-3 computes 1-2 and abandons the rest
of the line (a wrong answer, not a refused one); a unary-minus argument inflates
a function's arity so ABS(-9) is rejected; a comparison operator in a line's
final column is dropped; hex literals never survive the scanner; and the
"Reserved word in variable name" check is dead code.
Where the reference reaches undefined behaviour by a route that is defined in Go
-- an out-of-range shift, a negative string multiplier, integer division by zero
-- this raises instead of inheriting the UB. No golden case exercises any of
them.
The top-level CMakeLists shadows add_test, set_tests_properties and
add_custom_target around all three add_subdirectory calls. Without it libakerror's
tests land in our suite as Not Run, and its un-namespaced `coverage` target stops
a coverage build from configuring at all. Test targets are akbasic_test_<name>:
bare test_<name> collides with libakstdlib's, which is what broke libakgl's
configure in c2b16d3.
ctest 59/59; ASan+UBSan 59/59; 92.3% line and 96.9% function coverage; no
warnings under -Wall -Wextra. Branch coverage is not a target, for the reason
libakstdlib and libakgl both record: the akerror macros expand into large branch
trees at every call site.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
