Tachikoma
d5a0edd692
docs/20 builds the engine and the boundary: the startup order, the starfield, actors and collision, booting a DEF-only script, the issue #8 mode workaround, the custom update hook, first light, screens, and the headless harness. docs/21 builds the three shared structures and the AI: the host type tables, the actor binding, the randomness route around issue #16, the measured case against structure arguments (issue #36), the three language rules that shape the script, the maneuvers, the argued formation decision, the script-death policy, and the interop proof. Every fenced block runs under tests/docs_examples.sh in both build configurations; five new preludes carry the C fragments. docs/10 gains the 'Calling a function every frame' section the chapters lean on: the per-call akbasic_environment_zero() rule, the set_mode(RUN) workaround, the clear_error() revival, and the case for rebinding over structure arguments. Index rows and chapter counts updated. Co-authored-by: andrew <andrew@aklabs.net> Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01XiGgpHuXUm2mR4Wzndw3dc
79 lines
4.3 KiB
Markdown
79 lines
4.3 KiB
Markdown
# The akbasic guide
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akbasic is a BASIC interpreter in the style of **Commodore BASIC 7.0** — the dialect
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the C128 shipped with — and **Dartmouth BASIC**. It runs programs from a file or from
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an interactive prompt, and it is also a C library you can link into a game so that
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players can script it.
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These chapters follow the shape of the
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[C128 Programmer's Reference Guide](http://www.jbrain.com/pub/cbm/manuals/128/C128PRG.pdf):
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the language first, then each hardware area, then the reference sections. If you know
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BASIC 7.0 you can skip to **[Chapter 13](13-differences.md)**, which is the list of
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everything that behaves differently here and why. **[Chapter 14](14-architecture.md)** is
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the odd one out: it is about the interpreter rather than the language, for anyone
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embedding it, debugging it or changing it.
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**[Chapters 17](17-tutorial-breakout.md)** and **[18](18-tutorial-breakout-artwork.md)**
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are tutorials rather than reference: they build one complete game twice, two different
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ways, in numbered steps you can type in one at a time. Start with 17 — it needs nothing
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but the earlier chapters, and 18 assumes it. **[Chapters 20](20-tutorial-galaga.md)** and
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**[21](21-tutorial-galaga-enemies.md)** are the third tutorial, from the other side of
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the boundary: a C game on libakgl that embeds the interpreter as its enemy-behavior
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engine, for anyone whose question is "how do I put this in *my* game".
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## Chapters
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| **[1. Introduction](01-introduction.md)** | What akbasic is, what it is not, and how to build it |
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| **[2. Getting started](02-getting-started.md)** | The prompt, your first program, saving and loading |
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| **[3. The language](03-the-language.md)** | Variables, types, arrays, operators, expressions |
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| **[4. Control flow](04-control-flow.md)** | `IF`, `FOR`, `DO`, `GOSUB`, labels, `ON`, error trapping |
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| **[5. Strings and formatting](05-strings-and-formatting.md)** | String functions, `PRINT USING`, `PUDEF` |
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| **[6. Graphics](06-graphics.md)** | `GRAPHIC`, `DRAW`, `BOX`, `CIRCLE`, `PAINT`, shapes |
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| **[7. Sound](07-sound.md)** | `SOUND`, `PLAY`, `ENVELOPE`, `VOL`, `TEMPO` |
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| **[8. Sprites](08-sprites.md)** | `SPRITE`, `SPRSAV`, `MOVSPR`, collision |
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| **[9. Files and disk](09-files-and-disk.md)** | Channels, `DOPEN`, program storage |
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| **[10. Embedding](10-embedding.md)** | Driving the interpreter from C |
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| **[11. Verb reference](11-verb-reference.md)** | Every statement, alphabetically |
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| **[12. Function reference](12-function-reference.md)** | Every function, alphabetically |
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| **[13. Differences from BASIC 7.0](13-differences.md)** | What a C128 programmer needs to know |
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| **[14. Architecture](14-architecture.md)** | How the interpreter is put together, how to debug it, how to change it |
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| **[15. Error codes](15-error-codes.md)** | Appendix: every value `ER#` can hold and every error line the interpreter prints |
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| **[16. Structures](16-structures.md)** | `TYPE`, records, strict pointers, and sharing a C struct with an embedding host |
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| **[17. Tutorial: Breakout](17-tutorial-breakout.md)** | Build a whole game out of the text grid and two `DATA` sprites, in sixteen steps |
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| **[18. Tutorial: Breakout with artwork](18-tutorial-breakout-artwork.md)** | Build it again out of loaded artwork, powerups and a drawn colour HUD, in thirteen |
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| **[19. Menus and dialogs](19-user-interface.md)** | `MENU`, `DIALOG`, `HUD` and `UISTYLE` — the widgets, and who owns the keyboard |
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| **[20. Tutorial: GALAGA](20-tutorial-galaga.md)** | Build a C engine on libakgl that embeds the interpreter, boots a script and hands it an actor |
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| **[21. Tutorial: GALAGA enemies](21-tutorial-galaga-enemies.md)** | Share three C structs with the script, then write the wave's whole brain in BASIC |
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## The shortest possible start
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```sh norun
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$ cmake -S . -B build && cmake --build build
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$ ./build/basic
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```
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```basic repl
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10 FOR I# = 1 TO 5
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20 PRINT "HELLO " + I#
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30 NEXT I#
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RUN
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```
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```output
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HELLO 1
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HELLO 2
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HELLO 3
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HELLO 4
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HELLO 5
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READY
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```
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Two things in that program are not Commodore BASIC and will catch you out
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immediately: **variables carry a type suffix** (`I#` is an integer) and **`+`
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concatenates a string with a number**. Chapter 3 explains both.
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Every example in these chapters is executed by the test suite and its output
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compared byte for byte — see `MAINTENANCE.md` if you are editing them.
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