andrew/akbasic
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Honour a subscript in SSHAPE and GSHAPE

Browse Source 
`shape_variable()` took the identifier off the leaf and looked the variable up
without ever evaluating the subscript, and both verbs then addressed element
zero with a literal. So `SSHAPE SH$(2), ...` wrote the handle into `SH$(0)` and
`GSHAPE SH$(2)` stamped whatever was in `SH$(0)`.

Ordinary assignment and `PRINT` honour the subscript, which is what made this
expensive: a program keeping several saved shapes in an array got every one of
them resolving to the same element, silently, and the only symptom was that
every stamp came out as the last shape captured. The Breakout in examples/ keeps
its six brick stamps in six separate scalars for exactly this reason.

`SPRSAV` was the counter-example and is the model -- it evaluates its argument
and handles an array element correctly. The subscript resolution itself is now
shared: `collect_subscripts()` comes out of src/environment.c as
`akbasic_environment_collect_subscripts()`, so a verb taking a variable by name
resolves a subscript the same way assignment does rather than each verb deciding
for itself.

tests/graphics_verbs.c covers TODO.md's reduction -- which used to print
"[SHAPE:0] []" and now prints "[] [SHAPE:0]" -- and the case a program actually
wants: two shapes captured into two elements, each stamped back through its own,
asserted against the device log so a fix that merely made the strings look right
would not pass.

Chapter 18's trap 4 becomes history, and Chapter 6 says an array works.

TODO.md section 9 item 6, struck.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Andrew Kesterson
2026-08-02 00:10:24 -04:00
parent 694b446ce4
commit 8594d8471d
7 changed files with 122 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
TODO.md
View File

@@ -2704,8 +2704,15 @@ reduced against `build/basic`, the stdio build, unless it says otherwise.
This is worth a paragraph in chapter 13 beside the existing note, because "redraw it every
frame" is the advice there and it is not sufficient advice — the redraw also has to fit.
6. **`SSHAPE` and `GSHAPE` ignore the subscript on a string array element.** Needs a graphics
device, so this one is reduced against `build-akgl/basic`.
6. ~~**`SSHAPE` and `GSHAPE` ignore the subscript on a string array element.**~~ **Done** --
`shape_variable()` (`src/runtime_graphics.c`) now resolves the subscript the way
`SPRSAV` does, through a shared `akbasic_environment_collect_subscripts()` lifted out of
`src/environment.c` so that a verb taking a variable by name resolves one exactly as
assignment does. `tests/graphics_verbs.c` covers the reduction and the case a program
actually wants: two shapes captured into two elements and each stamped back by its own.
The original report, which needed a graphics device and was reduced against
`build-akgl/basic`:
```basic
DIM SH$(4)