Tachikoma
13f1df03ef
Adding native RND and ASC (ae2c702) made RND a function name, and a suffixed
identifier that collides with one is refused -- "SYNTAX ERROR Reserved word in
variable name". Three example programs held their PRNG output in a variable
called RND#, or a host field called RND%, and none of them had run since:
- examples/galaga/ bound RND% as a host field on both ENEMY and GAME. The
BASIC-visible name is ROLL% now; the C member stays `rnd`. This one was
caught by example_galaga and example_galaga_interop, which have been
failing.
- examples/breakout/characters/breakout.bas and examples/megademo/
megademo.bas both use RND# for their LCG output, renamed to ROLL#. Neither
is in any test, so neither failure was visible.
examples/breakout/sprites/breakout.bas was broken a second way: seven REM lines
the reader refuses. Worth recording that the ceiling is not the one the message
names -- src/sink_stdio.c fails when the read filled the buffer without seeing
a terminator, so with AKBASIC_MAX_LINE_LENGTH at 80 the message says "79
character limit" and the real maximum is 78, because a 79-character line leaves
no room for the newline. The sweeps that fixed the corpus and the megademo for
this did not reach this file. The seven comments are reflowed.
The prose went stale with the code. Chapter 21 said "there is no RND verb in
this dialect; issue #16 tracks adding one", chapter 17's historical aside
offered an LCG that no longer parses, and four REM blocks across the two games
said the same thing. All of them now say RND exists, and say why these programs
keep their own generator anyway: the sequence has to be reproducible for a
headless run to be the same game on every machine, which is what lets
interop_test.c assert exact counts.
Chapter 21 also gains the rule that bit them, since a reader writing a host
type will hit it: a host field name is a bare word and shares a namespace with
every verb and function.
None of this came from the submodule bump -- all three were already broken on
main. It was found by running the tutorial games, which nothing else does;
that gap is akbasic issue #58.
Verified: all three run clean under the dummy drivers, and 114/114 default,
116/116 with akgl.
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
Co-Authored-By: Claude Code (Claude Opus 5, claude-opus-5[1m]) <noreply@anthropic.com>
GALAGA — a C engine with akbasic embedded as its enemy brain
A GALAGA-style fixed shooter whose core engine is C on libakgl, with akbasic
linked in as the scripting engine that owns every enemy's behavior. One BASIC
script — galaga.bas, nothing but DEF functions and an END — is called
once per enemy per frame through a custom akgl_Actor update hook. Bullets,
collision, scoring and screens are C forever; everything an enemy decides is
BASIC.
This is the checked-in example behind two tutorial chapters, and the chapters are the intended way in:
- Chapter 20 — the engine and the boundary: from an empty file to a C game that boots a script and hands one actor to BASIC.
- Chapter 21 — the data
structures and the AI: from
SELF@to a full attacking wave.
It is an academic exercise demonstrating how such an embed is done, not a claim that it is the best way to write a GALAGA.
Building and running
The example builds when both example and graphics builds are on:
cmake -S . -B build-akgl -DAKBASIC_WITH_AKGL=ON
cmake --build build-akgl --target akbasic_example_galaga
build-akgl/akbasic_example_galaga
| Key | Does |
|---|---|
| Left / Right | move the ship |
| Space | fire (two shots on screen, the classic rule) |
| Return | choose a menu entry |
Flags
akbasic_example_galaga [--assets DIR] [--script PATH] [--frames N]
[--autoplay] [--screenshot PATH] [--screenshot-frame N]
--script points at a different enemy script, which is the whole point of the
architecture: edit galaga.bas, run again, no rebuild. --frames N with
--autoplay is the headless smoke test CI runs under the dummy SDL drivers;
the final log line reports frames, score, kills and shots per kind, and the
script-error count — a wave of dumb enemies still exits 0, and that count is
how you notice.
The files
| File | Owns |
|---|---|
galaga.h |
the shared structs — the whole boundary in one header |
main.c |
startup order, the frame loop, screens, the starfield |
script.c |
everything that touches the interpreter |
enemies.c |
wave table, formation grid, the enemy update hook |
player.c |
the ship, both bullet kinds, every collision |
galaga.bas |
every decision an enemy makes |
interop_test.c |
round-trip proof the boundary works, run by CTest |
assets/ |
sprite/character JSON, and Kenney CC0 art under assets/art/ |