Andrew Kesterson
c44a5903ec
0.9.0 is the akgl_ui subsystem: a vendored clay, an arena, menus, HUDs and dialogs, reached through a new akgl/ui.h this project does not include. Every header the akbasic_akgl target actually compiles against is byte-identical to 0.8.0, so unlike the 0.8.0 bump there is no sizeof to get wrong. The floor in include/akbasic/akgl.h moves to 0.9.0 anyway, on the standing rule that the soname carries MAJOR.MINOR while the major is 0. It does not configure as it stands. 0.9.0 moved eight test property calls off set_tests_properties -- correctly, because that command splits a semicolon-separated value and had been silently reducing its LD_LIBRARY_PATH prepend list to one directory -- onto set_property(TEST ...). This repository suppresses add_test() while it pulls its dependencies in, so those test names do not exist, and set_property errors on an unknown test name where set_tests_properties was silent: eight hard configure failures. Shadow set_property in its TEST form only; every other form has to pass through, since the dependencies set target and directory properties their own builds need. libakgl's status band grew to seven codes with AKGL_ERR_UI and it now owns 256 to 262, so the coordinated range map, docs/15-error-codes.md and both header comments follow. TODO.md section 5's persistent-drawing-layer item still stands: 0.9.0's arena draws inside the frame like everything else, and there is still no render-to-texture layer. Both configurations build and both suites pass -- 110/110 without libakgl, 111/111 with it, akgl_typing included. Co-Authored-By: Tachikoma (Claude Code Opus 5 1M) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL
The akbasic guide
akbasic is a BASIC interpreter in the style of Commodore BASIC 7.0 — the dialect the C128 shipped with — and Dartmouth BASIC. It runs programs from a file or from an interactive prompt, and it is also a C library you can link into a game so that players can script it.
These chapters follow the shape of the C128 Programmer's Reference Guide: the language first, then each hardware area, then the reference sections. If you know BASIC 7.0 you can skip to Chapter 13, which is the list of everything that behaves differently here and why. Chapter 14 is the odd one out: it is about the interpreter rather than the language, for anyone embedding it, debugging it or changing it.
Chapters 17 and 18 are tutorials rather than reference: they build one complete game twice, two different ways, in numbered steps you can type in one at a time. Start with 17 — it needs nothing but the earlier chapters, and 18 assumes it.
Chapters
| 1. Introduction | What akbasic is, what it is not, and how to build it |
| 2. Getting started | The prompt, your first program, saving and loading |
| 3. The language | Variables, types, arrays, operators, expressions |
| 4. Control flow | IF, FOR, DO, GOSUB, labels, ON, error trapping |
| 5. Strings and formatting | String functions, PRINT USING, PUDEF |
| 6. Graphics | GRAPHIC, DRAW, BOX, CIRCLE, PAINT, shapes |
| 7. Sound | SOUND, PLAY, ENVELOPE, VOL, TEMPO |
| 8. Sprites | SPRITE, SPRSAV, MOVSPR, collision |
| 9. Files and disk | Channels, DOPEN, program storage |
| 10. Embedding | Driving the interpreter from C |
| 11. Verb reference | Every statement, alphabetically |
| 12. Function reference | Every function, alphabetically |
| 13. Differences from BASIC 7.0 | What a C128 programmer needs to know |
| 14. Architecture | How the interpreter is put together, how to debug it, how to change it |
| 15. Error codes | Appendix: every value ER# can hold and every error line the interpreter prints |
| 16. Structures | TYPE, records, strict pointers, and sharing a C struct with an embedding host |
| 17. Tutorial: Breakout | Build a whole game out of the text grid and two DATA sprites, in sixteen steps |
| 18. Tutorial: Breakout with artwork | Build it again out of loaded artwork, powerups and a drawn colour HUD, in thirteen |
The shortest possible start
$ cmake -S . -B build && cmake --build build
$ ./build/basic
10 FOR I# = 1 TO 5
20 PRINT "HELLO " + I#
30 NEXT I#
RUN
HELLO 1
HELLO 2
HELLO 3
HELLO 4
HELLO 5
READY
Two things in that program are not Commodore BASIC and will catch you out
immediately: variables carry a type suffix (I# is an integer) and +
concatenates a string with a number. Chapter 3 explains both.
Every example in these chapters is executed by the test suite and its output
compared byte for byte — see MAINTENANCE.md if you are editing them.