Andrew Kesterson
694b446ce4
`RGR(1)` and `RGR(2)` gave the window in pixels and nothing gave columns, rows or the cell size -- so anything placing a character *and* a sprite at the same spot had to hardcode a number measured by hand against whatever font the host loaded. The Breakout in examples/ does exactly that, `CW# = 16`, and it is the one thing in that listing that breaks on a different font or window. **`RWINDOW` is BASIC 7.0's own answer and had never been implemented here.** `RWINDOW(0)` is the current text window's rows and `RWINDOW(1)` its columns. `RWINDOW(2)` reports a C128's 40 or 80 column screen mode, and this interpreter has neither -- refused by name, because answering 0 would be a plausible lie, which is worse than a refusal that says why. The cell size in pixels is `RGR(3)` and `RGR(4)`, beside the surface's own dimensions rather than on `RWINDOW`. Two reasons: a cell size is a fact about the surface, and `RWINDOW` reports the *window*, so dividing `RGR(1)` by a column count stops being right the moment a program calls `WINDOW`. Both read a new optional `grid` entry point on `akbasic_TextSink` -- columns, rows, cell width, cell height -- implemented by the akgl sink and forwarded by the tee, in the shape `moveto` and `window` already had. NULL everywhere else, so both verbs refuse by name against a sink with no grid. `akbasic_sink_init_ stdio()` clears it for the same reason it now clears the other two. Measured on the standalone build: `RGR(3)` answers 16 and `RWINDOW` answers 50 columns by 37 rows -- the three numbers the Breakout listing had written out as constants -- and `RWINDOW` follows a `WINDOW` call while `RGR(3)` does not. tests/console_verbs.c drives the answers through a stand-in sink with a grid, since the harness sink is stdio and has none; tests/graphics_verbs.c covers the new `RGR` fields, their refusal, and the moved range bound. The `c excerpt=` block in docs/10-embedding.md moves with the header, which is `docs_examples` doing its job. TODO.md section 6 item 31's second half, struck. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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12. Function reference
Every function, alphabetically, generated from the interpreter's own dispatch table.
A function is called with parentheses and yields a value; it cannot stand alone as a statement. The arity column is how many arguments it takes — the interpreter checks it, so a call with the wrong number is a syntax error rather than a surprise.
| Function | Args | Form | What it gives |
|---|---|---|---|
ABS |
1 | ABS(n) |
The absolute value of an integer or float. |
ATN |
1 | ATN(n) |
Arctangent, in radians. |
BUMP |
1 | BUMP(1) |
Which sprites have collided, as a bitmask. Reading clears it. |
CHR |
1 | CHR(n) |
The character for a Unicode code point, as a string. |
COS |
1 | COS(n) |
Cosine, in radians. |
ERR |
1 | ERR(n) |
The message text for an error code. ERR(ER#) names the last one. |
HEX |
1 | HEX(n) |
An integer as hexadecimal text. |
INSTR |
2 | INSTR(A$, B$) |
Where B$ appears in A$, counting from zero, or -1. |
LEFT |
2 | LEFT(A$, n) |
The leftmost n characters. Clamped to the string's length. |
LEN |
1 | LEN(x) |
The length of a string, or the element count of an array. |
LOG |
1 | LOG(n) |
Natural logarithm. |
MID |
3 | MID(A$, start, len) |
A substring, counting from zero. |
MOD |
2 | MOD(a, b) |
The remainder of a / b. Integers only. |
PEEK |
1 | PEEK(addr) |
The byte at a real address. |
POINTER |
1 | POINTER(V) |
The address of a variable's value. |
POINTERVAR |
1 | POINTERVAR(V) |
The address of the variable structure itself, metadata included. |
RAD |
1 | RAD(n) |
Degrees converted to radians. |
RGR |
1 | RGR(f) |
The GRAPHIC mode (0), the drawing surface's width (1) or height (2) in pixels, or a character cell's width (3) or height (4). |
RIGHT |
2 | RIGHT(A$, n) |
The rightmost n characters. Clamped. |
RWINDOW |
1 | RWINDOW(f) |
The current text window's rows (0) or columns (1). Field 2 is a C128 screen mode and is refused. |
RSPCOLOR |
1 | RSPCOLOR(n) |
One of SPRCOLOR's two shared registers, 1 or 2. |
RSPPOS |
2 | RSPPOS(n, f) |
A sprite's x (0), y (1) or speed (2). |
RSPRITE |
2 | RSPRITE(n, f) |
One of a sprite's SPRITE settings, in SPRITE's argument order. |
SGN |
1 | SGN(n) |
-1, 0 or 1 according to the sign. |
SHL |
2 | SHL(n, bits) |
Shift left. |
SHR |
2 | SHR(n, bits) |
Shift right. |
SIN |
1 | SIN(n) |
Sine, in radians. |
SPC |
1 | SPC(n) |
A string of n spaces. |
STR |
1 | STR(n) |
A number as a string. |
TAN |
1 | TAN(n) |
Tangent, in radians. |
VAL |
1 | VAL(A$) |
A string as a number. Refuses text that is not one. |
XOR |
2 | XOR(a, b) |
Bitwise exclusive or. |
Reserved variables
Two things a C128 exposes as bare names are ordinary global variables here, because this dialect has no variable name without a type suffix:
| Here | On a C128 | Holds |
|---|---|---|
ER# |
ER |
the code of the last trapped error |
EL# |
EL |
the line it happened on |
TI# |
TI |
jiffies — sixtieths of a second — since the host's clock started |
TI$ |
TI$ |
the same time as HHMMSS |
ER# carries this interpreter's error code, not a Commodore error number. There is no
correspondence to reproduce — the errors raised here are not the errors a 1985 ROM
raised — so print ERR(ER#) rather than the number. Chapter 15
lists every value it can hold.