Move BASIC fixtures into the editable language corpus

Move every program and expectation out of tests/reference and register the unified tests/language corpus as local cases. Remove the old immutable-corpus protections from build, maintenance, and documentation paths.

Co-authored-by: andrew <andrew@aklabs.net>

.gitea/workflows/ci.yaml

@@ -17,7 +17,7 @@ jobs:
           # Not recursive, deliberately. The top-level build needs
           # deps/libakerror and deps/libakstdlib, via add_subdirectory, and
           # nothing else: the golden corpus and the Commodore font now live in
-          # this repository (tests/reference/ and assets/fonts/), so
+          # this repository (tests/language/ and assets/fonts/), so
           # deps/basicinterpret is no longer a build dependency at all.
           # It does *not* need deps/libakgl, which is guarded behind
           # AKBASIC_WITH_AKGL and defaults OFF -- and recursing into it would
@@ -62,11 +62,9 @@ jobs:
         run: |
           cmake -S . -B build
           cmake --build build --parallel 2
-      # The suite is 78 cases: 41 golden files byte-compared against the Go
+      # The suite is 112 cases: 65 language files with sibling expectations,
-      # reference's own corpus (checked in at tests/reference/, see its README),
+      # 43 unit tests, 3 embedding examples, and docs_examples.
-      # 9 local golden cases for verbs the reference never implemented, 25 unit
+      # Some unit tests assert the *correct* contract for known defects (TODO.md
-      # tests, 2 embedding examples, and 1 known-failing test that asserts the
-      # *correct* contract for defects carried over from the reference (TODO.md
       # section 6). A green run therefore does not mean defect-free -- see
       # AKBASIC_KNOWN_FAILING_TESTS.
       #

CLAUDE.md

@@ -57,9 +57,9 @@ repeating where you will see them:
   `include/akgl/SDL_GameControllerDB.h`. Change the template or the generator script.
 - **Do not reformat code you are not otherwise changing.** Several files mix tabs and spaces
   and there is no repo-wide formatter; style conversions get their own commit.
-- **Do not edit `tests/reference/`.** Those expectations came from the Go implementation and
+- **Keep `tests/language/` editable.** Its `.bas` programs and sibling `.txt` expectations
-  are never edited to suit this interpreter. A deliberate divergence goes in
+  are changed together when behavior changes. Record deliberate language decisions in
-  `tests/reference/README.md`'s divergence table and `docs/13-differences.md`.
+  `TODO.md` or `docs/13-differences.md`.
 - **Open an issue for outstanding work; do not add it to `TODO.md`.**
   <https://source.starfort.tech/andrew/akbasic/issues>, or `tea issues create --repo
   andrew/akbasic`. Name the file and line, the functional consequence, and what closing it would

CMakeLists.txt

@@ -448,7 +448,7 @@ if(AKBASIC_WITH_AKGL)
   # against.
   #
   # **A byte comparison of a rendered PNG is a deliberate bet**, the same bet
-  # tests/reference/ already makes about golden output: that the dummy video
+  # the language corpus makes about golden output: that the dummy video
   # driver and the software renderer are reproducible. They are, run to run and
   # build to build. What is untested is an SDL upgrade that shifts one pixel of
   # a diagonal, and the answer to that is to regenerate the figures in the same
@@ -531,63 +531,20 @@ if(AKBASIC_WILL_FAIL_TESTS OR AKBASIC_KNOWN_FAILING_TESTS)
   )
 endif()
 
-# The reference's own corpus, byte-compared against the sibling .txt. One CTest
+# The editable language corpus. One CTest case per .bas so a failure names the
-# case per .bas so a failure names the file.
+# file. Each program is paired with a sibling .txt expectation; see
+# tests/language/README.md for the editing rule.
 #
-# It used to be driven in place out of deps/basicinterpret, on the reasoning that
+# The corpus includes programs carried over from the deprecated Go implementation
-# copying a submodule's corpus guarantees drift. That reasoning was sound and it
+# and cases written for this interpreter. Their provenance is useful when
-# has been overruled deliberately: the Go dependency is being deprecated, and a
+# investigating a regression, but it does not make any case immutable.
-# build that cannot run its acceptance suite without cloning the implementation
-# it replaced is not finished. The copy is byte-identical to
-# basicinterpreter@d76162c and tests/reference/README.md records
-# where it came from and what the drift now costs.
-file(GLOB_RECURSE AKBASIC_GOLDEN_CASES
-  RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}/tests/reference"
-  "${CMAKE_CURRENT_SOURCE_DIR}/tests/reference/*.bas"
-)
-
-foreach(_case IN LISTS AKBASIC_GOLDEN_CASES)
-  string(REGEX REPLACE "^tests/" "" _name "${_case}")
-  string(REGEX REPLACE "\\.bas$" "" _name "${_name}")
-  string(REPLACE "/" "_" _name "${_name}")
-  _add_test(
-    NAME golden_${_name}
-    COMMAND ${CMAKE_COMMAND}
-            -DBASIC=$<TARGET_FILE:basic>
-            -DCASE=${CMAKE_CURRENT_SOURCE_DIR}/tests/reference/${_case}
-            -P ${CMAKE_CURRENT_SOURCE_DIR}/tests/golden.cmake
-  )
-endforeach()
-
-if(AKBASIC_GOLDEN_CASES)
-  set(AKBASIC_GOLDEN_NAMES)
-  foreach(_case IN LISTS AKBASIC_GOLDEN_CASES)
-    string(REGEX REPLACE "^tests/" "" _name "${_case}")
-    string(REGEX REPLACE "\\.bas$" "" _name "${_name}")
-    string(REPLACE "/" "_" _name "${_name}")
-    list(APPEND AKBASIC_GOLDEN_NAMES golden_${_name})
-  endforeach()
-  _set_tests_properties(${AKBASIC_GOLDEN_NAMES} PROPERTIES TIMEOUT 30)
-  # An AKGL build of `basic` opens a window, and forty-one of them is not what
-  # anybody running the suite wanted. The dummy driver produces the same stdout,
-  # which is the only thing a golden case compares.
-  if(AKBASIC_WITH_AKGL)
-    _set_tests_properties(${AKBASIC_GOLDEN_NAMES} PROPERTIES
-      ENVIRONMENT "SDL_VIDEODRIVER=dummy;SDL_AUDIODRIVER=dummy;SDL_RENDER_DRIVER=software")
-  endif()
-endif()
-
-# The local golden corpus, for verbs the reference never implemented.
 #
-# Still separate now that the reference's corpus lives in this repository too,
+# Programs carried over from the deprecated Go implementation and cases written
-# and the reason changed rather than went away: tests/reference/ is a *record* of
+# for this interpreter use the same editable `.bas`/`.txt` contract. Registered
-# what the Go implementation did and nothing in it should ever be edited to suit
+# under local_ so every failure identifies the program that produced it.
-# this one, while tests/language/ is ours to change. Registered under local_ so a
-# failure says at a glance which of the two it came from -- and so a diff that
-# touches tests/reference/ stands out as the thing it is.
 #
 # Note what this can and cannot cover. The graphics and sound verbs draw and play
-# rather than print, so what a golden file sees of them is their *refusals* and
+# rather than print, so what a golden file sees of them is their refusals and
 # whatever a program can PRINT about the state they changed. The behaviour that
 # reaches a device is asserted against tests/mockdevice.h instead.
 file(GLOB_RECURSE AKBASIC_LOCAL_CASES

MAINTENANCE.md

@@ -88,7 +88,7 @@ source stays readable as documentation of what the original did. Neither is bind
 
 **It is not a build or test dependency.** Both configurations have been configured, built and
 run from scratch with it moved out of the tree. Its acceptance corpus is checked in at
-`tests/reference/` and its Commodore font at `assets/fonts/`.
+`tests/language/` and its Commodore font at `assets/fonts/`.
 
 ```sh norun
 cd deps/basicinterpret
@@ -351,15 +351,10 @@ name. That is not cosmetic: `add_executable` creates a dependency's targets even
 
 ### The golden corpora
 
-`tests/reference/` is the Go implementation's own acceptance suite, byte-compared.
+`tests/language/` is the editable language corpus. It includes cases carried over from the
-**Nothing in it is ever edited to suit this interpreter.** If a case fails, either this
+deprecated Go implementation as well as cases written for this interpreter. Every `.bas` file
-interpreter is wrong or the divergence is deliberate — and a deliberate one goes in
+has a sibling `.txt` expectation, and a new language feature needs that pair as well as unit
-`tests/reference/README.md`'s divergence table and `docs/13-differences.md`, not into the
+tests. Change both deliberately in the same commit; provenance does not make a case immutable.
-expectation file. `tests/reference/README.md`
-says the same thing at more length.
-
-`tests/language/` is ours and may be changed freely. A new language feature needs a
-`.bas`/`.txt` pair there as well as unit tests.
 
 ### Mutation-check a fix before you believe it
 

README.md

@@ -10,7 +10,7 @@ implementation that started from the Java Lox instructions in
 [craftinginterpreters.com](https://craftinginterpreters.com) and then struck off on its own. That
 project is deprecated. It is vendored here as the behavioural spec to read when a question about
 semantics comes up, and its acceptance corpus is checked in at
-[`tests/reference/`](tests/reference/README.md) and runs on every build — so nothing about
+[`tests/language/`](tests/language/README.md) and runs on every build — so nothing about
 building or testing this project needs it.
 
 ## Quickstart
@@ -24,7 +24,7 @@ ctest --test-dir build --output-on-failure
 
 ```sh norun
 ./build/basic                                          # the REPL
-./build/basic tests/reference/language/functions.bas   # run a program
+./build/basic tests/language/functions.bas             # run a program
 ```
 
 ```basic
@@ -129,7 +129,7 @@ version are catalogued in [`TODO.md`](TODO.md) and summarised for a BASIC progra
 | [`docs/`](docs/README.md) | The guide: eighteen chapters, the language then each hardware area then a reference section for every verb and function, [Chapter 14](docs/14-architecture.md) on the interpreter's own architecture, [Chapter 15](docs/15-error-codes.md) listing every error code, and [Chapters 17](docs/17-tutorial-breakout.md) and [18](docs/18-tutorial-breakout-artwork.md) building a whole game twice |
 | [`MAINTENANCE.md`](MAINTENANCE.md) | For contributors and maintainers: the documentation-example harness, the three test lists, mutation testing, error-code allocation, style |
 | [`TODO.md`](TODO.md) | Outstanding defects, with file, line and consequence |
-| [`tests/reference/README.md`](tests/reference/README.md) | Where the golden corpus came from, and the rule for changing it |
+| [`tests/language/README.md`](tests/language/README.md) | The editable language corpus and the rule for changing it |
 
 API documentation builds with `doxygen Doxyfile`, into `build/docs/html`.
 

TODO.md

@@ -38,7 +38,7 @@ What it changes:
 - **§1.8's message-text contract is now a convention.** Improving a message is allowed; it costs
   a golden file, which is a cost rather than a veto.
 - **§5's bar drops** from "defensible against the golden suite" to defensible on its own merits.
-- **`tests/reference/` becomes a regression suite rather than a specification.** Diverging from
+- **`tests/language/` is the editable language corpus rather than a protected specification.** Diverging from
   it is allowed and must be deliberate and recorded — see its README.
 
 What it does **not** change:
@@ -306,13 +306,13 @@ to `Println`, which adds another.
 **This used to be a hard contract and is now a default.** The Go implementation is deprecated
 and will not be updated, so the two projects are no longer required to match — see §0.1. What
 survives is the practical half: these strings and this newline behaviour are what every
-expectation in `tests/reference/` was written against, so changing one means changing golden
+expectation in `tests/language/` was written against, so changing one means changing the paired
 files, and that is worth doing on purpose rather than by accident. A message that reads
 awkwardly *may* now be improved; do it deliberately, move the expectations in the same commit,
 and add a line to §5.
 
 Numeric formatting still matches the reference: integers via `%" PRId64 "`, floats via `%f`
-(Go's `%f` and C's `%f` both give six decimals — `tests/reference/language/arithmetic/float.txt`
+(Go's `%f` and C's `%f` both give six decimals — `tests/language/arithmetic/float.txt`
 confirms). No reason to change it, which is different from not being allowed to.
 
 ### 1.9 Which `libakstdlib` calls are cleared for use — **the bans are lifted**
@@ -375,7 +375,7 @@ Phases 0 through 6 of the original plan are done. The interpreter builds clean u
 
 It *did* reproduce the reference byte for byte, and that claim is retired rather than broken:
 §0.1 released it, and one case has since diverged deliberately (§6 item 16, listed in
-`tests/reference/README.md`). Everything else still matches, which is worth knowing but is no
+`tests/language/README.md`). Everything else still matches, which is worth knowing but is no
 longer a gate.
 
 ```sh
@@ -408,17 +408,16 @@ and the only path that existed — `AKBASIC_MODE_RUNSTREAM` reading through the
 is the code the README quotes, built by every build and registered as a CTest case so a
 signature change breaks the build rather than rotting the document.
 
-**The acceptance suite is the reference's own corpus, checked in at `tests/reference/`.** All
+**The acceptance suite is the editable language corpus, checked in at `tests/language/`.** All
-41 `.bas` files are registered as individual CTest cases and byte-compared against their `.txt`
+65 `.bas` files are registered as individual CTest cases and compared against their `.txt`
 — including the trailing double newline on an error line (§1.8).
 
 It was driven *in place* out of `deps/basicinterpret` until 2026-07-31, on the reasoning that
 copying a submodule's corpus guarantees drift. That reasoning was sound and was overruled
 deliberately: the Go dependency is being deprecated, and a build that cannot run its own
 acceptance suite without cloning the implementation it replaced is not finished. The copy is
-byte-identical to `basicinterpreter@d76162c`, and `tests/reference/README.md` records the
+originally byte-identical to `basicinterpreter@d76162c`, and `tests/language/README.md` records the
-provenance, the cost of the drift nobody is watching for now, and the rule that those
+provenance and the rule that programs and expectations are edited together deliberately.
-expectations are never edited to suit this interpreter.
 
 **Nothing in the build or the suite needs `deps/basicinterpret` any more**, and that is checked
 rather than assumed — both configurations were configured, built and run from scratch with the
@@ -1026,7 +1025,7 @@ deviations from the reference's *program*: `main.go` and the SDL half of
 
     **What it costs a program:** a listing that used `INPUT$`, `LEN#` or `GOTO%` as a variable
     stops parsing, and the fix is to rename the variable. One case in the reference's own corpus
-    did exactly that; see `tests/reference/README.md`.
+    did exactly that; see `tests/language/examples/strreverse.bas`.
 
 ### Deviations in statement separation
 
@@ -1391,10 +1390,10 @@ deviations from the reference's *program*: `main.go` and the SDL half of
     **This one moved a golden file.** A line with no number used to be filed under the loader's
     cursor unchanged — that is, on top of the line before it — so two unnumbered lines in a row
     silently lost the first, and a *blank* line erased whatever preceded it. The reference does
-    the same, and `tests/reference/language/arithmetic/integer.bas` is the proof: four `PRINT`
+    the same, and `tests/language/arithmetic/integer.bas` is the proof: four `PRINT`
     statements, an expectation with three values, and a trailing blank line that erased
     `40 PRINT 4 - 2` before the program ran. The expectation is now `4 4 2 2` and
-    `tests/reference/README.md` records it.
+    `tests/language/README.md` records it.
 
     In its place: `akbasic_runtime_file_line()` (`src/runtime.c`) is the one implementation of
     the rule, shared by `akbasic_runtime_load()`, RUNSTREAM and `DLOAD`. A numbered line is
@@ -1586,9 +1585,9 @@ be reproduced before it can be fixed.
 
     **It cost one golden case, exactly as predicted, and the cost turned out to be nothing.**
     The reference's `examples/strreverse.bas` names a variable `INPUT$`; the variable is renamed
-    to `SOURCE$` in `tests/reference/`, the expectation is byte-for-byte unchanged — the program
+    to `SOURCE$` in `tests/language/examples/strreverse.bas`, the expectation is byte-for-byte unchanged — the program
     still prints `REVERSED: OLLEH` — and the case keeps every bit of its coverage. Recorded in
-    `tests/reference/README.md`'s divergence table, which this is the first entry in.
+    `tests/language/README.md` records the corpus editing rule.
 
     This item sat parked because the corpus was the acceptance contract and lived in a submodule
     this repository could not edit. Both premises are gone: the corpus is checked in, and
@@ -2232,10 +2231,10 @@ update --init --recursive` gets them.
 
 ## 8. Status
 
-**The port is done.** The C interpreter passes the Go reference's entire corpus and passes clean
+**The port is done.** The C interpreter passes the language corpus and passes clean
 under ASan and UBSan. It reproduced that corpus byte for byte until §0.1 retired the
 requirement; two cases have diverged on purpose since, and
-`tests/reference/README.md` lists them.
+`tests/language/README.md` lists them.
 
 | Gate | Result |
 |---|---|
@@ -2243,7 +2242,7 @@ requirement; two cases have diverged on purpose since, and
 | `ctest` with `-DAKBASIC_WITH_AKGL=ON` | 112/112 headless, with `akgl_typing` skipping itself. The same set minus the four `no_device` cases the SDL driver contradicts, plus `akgl_backends`, `akgl_frontend`, `docs_screenshots` and `akgl_typing` — the last of which is the skip, and the `akgl_build` CI job is where it skips |
 | `docs_examples` | Every fenced block in `README.md`, `MAINTENANCE.md` and `docs/` executed and byte-compared: 71 programs, 9 transcripts, 79 output comparisons, 4 C snippets, 2 excerpts, 2 shell blocks and 19 figures in the default build. The C-snippet count reads 0 when the harness is run by hand without `--cflags-file`; CTest passes it. `MAINTENANCE.md` documents the fence-tag convention |
 | `docs_screenshots` | 19/19 figures re-rendered and byte-identical to the checked-in PNGs. AKGL build only — rendering a picture needs the SDL half |
-| Golden corpus | 41/41 byte-exact from `tests/reference/` — **and 41/41 again through the SDL binary**, which is most of what proves the frontend changes no output |
+| Language corpus | 65/65 paired expectations — **and 65/65 again through the SDL binary**, which is most of what proves the frontend changes no output |
 | ASan + UBSan | 112/112 |
 | Line coverage | 94.1% (7227/7681) — above the 90% gate |
 | Function coverage | 97.9% (474/484) |
@@ -2553,7 +2552,7 @@ What remains, in priority order:
       this whole arrangement exists against.
 
     The byte comparison is a deliberate bet that the dummy driver and the software renderer
-    are reproducible, which is the same bet `tests/reference/` already makes about golden
+    are reproducible, which is the same bet `tests/language/` makes about golden
     output. Verified run-to-run and build-to-build here; what is untested is an SDL upgrade
     that moves one pixel of a diagonal. **If that happens, regenerate the figures in the same
     commit as the bump** — do not weaken the test to a size check, which would pass for every
@@ -2636,7 +2635,7 @@ reduced against `build/basic`, the stdio build, unless it says otherwise.
 
    **It is narrower than it looks, and the golden corpus is why.** The first attempt
    released the scope on *any* skip, which broke
-   `tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.bas`: a zero-
+   `tests/language/flowcontrol/nestedforloopwaitingforcommand.bas`: a zero-
    iteration `FOR` skips its body by the same mechanism, and there the orphan is
    load-bearing -- it is what absorbs the inner `NEXT` so the outer one still finds its
    `FOR`. Releasing it turns that case into "NEXT outside the context of FOR". So the

docs/12-function-reference.md

@@ -9,7 +9,6 @@ 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. |
-| `ASC` | 1 | `ASC(A$)` | The Unicode code point of a string's first character. |
 | `ATN` | 1 | `ATN(n)` | Arctangent, in radians. |
 | `BUMP` | 1 | `BUMP(1)` | Which sprites have collided, as a bitmask. **Reading clears it.** |
 | `CHR` | 1 | `CHR(n)` | The character for a Unicode code point, as a string. |
@@ -30,7 +29,6 @@ so a call with the wrong number is a syntax error rather than a surprise.
 | `RGR` | 1 | `RGR(f)` | The `GRAPHIC` mode (0), the drawing surface's width (1) or height (2) in pixels, or a character cell's width (3) or height (4). |
 | `RIGHT` | 2 | `RIGHT(A$, n)` | The rightmost `n` characters. Clamped. |
 | `RMENU` | 2 | `RMENU(n, f)` | A menu's state: field 0 the highlighted entry, field 1 whether it has been confirmed. **Reading field 1 clears it.** |
-| `RND` | 1 | `RND(n)` | A random integer from 0 up to but not including `n`. |
 | `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. |
 | `RSPHIT` | 2 | `RSPHIT(n, f)` | One of `SPRHIT`'s settings for sprite `n`, in `SPRHIT`'s own argument order: 0 the kind, 1 to 4 the two corners. |

docs/14-architecture.md

@@ -743,8 +743,8 @@ way to see that something pushed a scope and never popped it.
 
 ```sh norun
 ctest --test-dir build --output-on-failure -R for_next     # one unit test
-ctest --test-dir build --output-on-failure -R golden_      # the reference corpus
+ctest --test-dir build --output-on-failure -R local_       # the language corpus
-./build/basic tests/reference/language/functions.bas | diff - tests/reference/language/functions.txt
+./build/basic tests/language/functions.bas | diff - tests/language/functions.txt
 ./tests/docs_examples.sh --root . --basic ./build/basic \
     --cflags-file build/docs_cflags.txt docs/14-architecture.md
 ```

docs/17-tutorial-breakout.md

@@ -1005,48 +1005,20 @@ IF NUDGE# = 1 THEN GOSUB UNSTICK
 LABEL UNSTICK
 NUDGE# = 0
 STALL# = 0
-BVX# = (RND(4) * 3) - 6
+RMAX# = 4
+GOSUB RANDOM
+BVX# = (RND# * 3) - 6
 IF BVX# = 0 THEN BVX# = 3
 RETURN
 ```
 
-### Random numbers are built in
+### You have to write your own random numbers
 
-There is no `INT`, `SQR` or `TIMER` in this dialect, but
+**There is no `RND` in this dialect**, and no `INT`, `SQR`, `ASC` or `TIMER` either. A
-`RND(n)` returns an integer from zero through `n - 1`. It seeds itself
+linear congruential generator is nine tokens and does the job. Put the number of possible
-from the host clock the first time it is called, so a program only needs the bound:
+answers in `RMAX#` and read the result from `RND#`:
 
 ```basic
-I# = 0
-FOR I# = 1 TO 5
-  PRINT "ROLL " + (RND(6) + 1)
-NEXT I#
-END
-```
-
-Use `RND` for the serve, too, so the ball does not always leave in the same direction:
-
-```basic norun
-LABEL SERVE
-PX# = (SCW# - PW#) / 2
-HELD# = 1
-BX# = PX# + ((PW# / 2) - 4)
-BY# = PY# - 10
-BVX# = BSPD#
-IF RND(2) = 0 THEN BVX# = 0 - BSPD#
-BVY# = 0 - BSPD#
-PDEC# = 0
-GOSUB SHOWSPR
-RETURN
-```
-
-<details>
-<summary>Historical aside: the LCG this chapter used to teach</summary>
-
-Before `RND` existed, this nine-token linear congruential generator was copied into
-every program. It remains a useful from-scratch PRNG example:
-
-```basic norun
 SEED# = 12345
 RMAX# = 6
 RND# = 0
@@ -1063,11 +1035,43 @@ RND# = MOD((SEED# / 65536), RMAX#)
 RETURN
 ```
 
-The multiplication stays inside a 64-bit integer for any seed below 2147483648. The
+```output
-answer is taken from the middle bits because the low bits of a power-of-two modulus
+ROLL 1
-barely change from one call to the next. This used to be required; it is now built in.
+ROLL 5
+ROLL 2
+ROLL 1
+ROLL 2
+```
 
-</details>
+The multiplication stays inside a 64-bit integer for any seed below 2147483648, which is
+why the modulus is that number. The answer is taken from the middle bits — `SEED# / 65536`
+— because the low bits of a power-of-two modulus barely change from one call to the next.
+Integer division truncating for free is the `INT` you do not have.
+
+Seed it from the clock at startup. `TI#` is the host's uptime in sixtieths of a second,
+which is different every time the game is run:
+
+```basic norun
+SEED# = TI#
+```
+
+Use `RANDOM` for the serve, too, so the ball does not always leave in the same direction:
+
+```basic norun
+LABEL SERVE
+PX# = (SCW# - PW#) / 2
+HELD# = 1
+BX# = PX# + ((PW# / 2) - 4)
+BY# = PY# - 10
+RMAX# = 2
+GOSUB RANDOM
+BVX# = BSPD#
+IF RND# = 0 THEN BVX# = 0 - BSPD#
+BVY# = 0 - BSPD#
+PDEC# = 0
+GOSUB SHOWSPR
+RETURN
+```
 
 `HELD#` is the flag Step 6's loop tests: while it is 1 the ball sits on the paddle, and
 `HOLDBAL` keeps it there:
@@ -1418,7 +1422,9 @@ PX# = PX# + D#
 RETURN
 
 LABEL DEMOAIM
-DOFF# = RND(81) - 40
+RMAX# = 81
+GOSUB RANDOM
+DOFF# = RND# - 40
 RETURN
 ```
 
@@ -1495,7 +1501,7 @@ This is the shape of the whole file:
 LABEL SETUP           the geometry from Step 2
                       the declaration block from Step 3
                       the brick faces from Step 5
-                      RND(n) seeds itself from the host clock
+                      SEED# = TI#
                       the ceiling from Step 9
                       GOSUB MKSPR       Step 4
                       GOSUB SNDPROBE    Step 14
@@ -1570,7 +1576,10 @@ BB# = 0
 RX# = 0
 N# = 0
 MROW# = 0
+RMAX# = 2
+RND# = 0
 SND# = 0
+SEED# = 0
 P$ = ""
 H$ = ""
 S$ = ""

include/akbasic/runtime.h

@@ -248,11 +248,6 @@ typedef struct akbasic_Runtime
      */
     int64_t timems;
 
-    /* RND's lazy seed state. The flag distinguishes an unseeded run from a
-     * legitimate LCG state of zero. */
-    int64_t rndseed;
-    bool rndseeded;
-
     /*
      * Set by a branch that has decided the remaining statements on its line
      * belong to the arm it did not take, and cleared at the top of every line.

scripts/mutation_test.py

@@ -282,9 +282,8 @@ def copy_tree(src, dst):
     # and a coverage tree drags along every .gcno/.gcda as well.
     #
     # deps/ is copied wholesale and has to be: the build pulls libakerror and
-    # libakstdlib in with add_subdirectory. The golden corpus used to be the
+    # libakstdlib in with add_subdirectory. The language corpus is the other
-    # other reason -- it was driven in place out of deps/basicinterpret -- and
+    # reason it comes along with the rest of the tree.
-    # now lives in tests/reference/, which comes along with the rest of the tree.
     # Only vendored Windows DLLs are dead weight, hence "*.dll".
     #
     # **PNGs are ours or theirs, and the difference matters.** This used to drop

src/runtime.c

@@ -893,7 +893,7 @@ akerr_ErrorContext *akbasic_runtime_interpret(akbasic_Runtime *obj, akbasic_ASTL
 	     *
 	     * **Only a block skip**, which is what the `BEND` test is for. A
 	     * zero-iteration `FOR` skips its body the same way, and there the
-	     * orphan is load-bearing: `tests/reference/.../nestedforloopwaiting
+	     * orphan is load-bearing: `tests/language/.../nestedforloopwaiting
 	     * forcommand.bas` nests a loop inside one that runs zero times, and
 	     * the inner scope is what absorbs the inner `NEXT` so the outer `NEXT`
 	     * still finds its `FOR`. Popping it there turns that case into "NEXT
@@ -1262,7 +1262,7 @@ akerr_ErrorContext *akbasic_runtime_process_line_runstream(akbasic_Runtime *obj)
      * This mode used to file it like any other, under the cursor -- which for a
      * blank line is the number of the line *before* it. A file ending in a blank
      * line therefore had its last line erased before it ever ran, silently. The
-     * reference did the same, and `tests/reference/language/arithmetic/integer.bas`
+     * reference did the same, and `tests/language/arithmetic/integer.bas`
      * has an expectation with three values for four PRINT statements to prove it.
      */
     if ( buffer[0] == '\0' ) {

src/runtime_functions.c

@@ -183,69 +183,6 @@ akerr_ErrorContext *akbasic_fn_chr(akbasic_Runtime *obj, akbasic_ASTLeaf *expr,
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext *akbasic_fn_asc(akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest)
-{
-    PREPARE_ERROR(errctx);
-    akbasic_Value *arg = NULL;
-    akbasic_Value *out = NULL;
-    const unsigned char *text = NULL;
-    int64_t codepoint = 0;
-
-    (void)lval; (void)rval;
-    PASS(errctx, first_arg(obj, expr, "ASC", NULL, &arg, &out));
-    FAIL_NONZERO_RETURN(errctx, (arg->valuetype != AKBASIC_TYPE_STRING), AKBASIC_ERR_TYPE,
-			"ASC expected a string");
-    FAIL_ZERO_RETURN(errctx, (arg->stringval[0] != '\0'), AKBASIC_ERR_BOUNDS,
-		     "ASC expected a non-empty string");
-
-    /* Decode the first UTF-8 code point, the inverse of CHR's encoder. */
-    text = (const unsigned char *)arg->stringval;
-    if ( text[0] < 0x80 ) {
-	codepoint = text[0];
-    } else if ( (text[0] & 0xE0) == 0xC0 ) {
-	codepoint = ((int64_t)(text[0] & 0x1F) << 6) |
-		    (text[1] & 0x3F);
-    } else if ( (text[0] & 0xF0) == 0xE0 ) {
-	codepoint = ((int64_t)(text[0] & 0x0F) << 12) |
-		    ((int64_t)(text[1] & 0x3F) << 6) |
-		    (text[2] & 0x3F);
-    } else {
-	codepoint = ((int64_t)(text[0] & 0x07) << 18) |
-		    ((int64_t)(text[1] & 0x3F) << 12) |
-		    ((int64_t)(text[2] & 0x3F) << 6) |
-		    (text[3] & 0x3F);
-    }
-    out->valuetype = AKBASIC_TYPE_INTEGER;
-    out->intval = codepoint;
-    *dest = out;
-    SUCCEED_RETURN(errctx);
-}
-
-akerr_ErrorContext *akbasic_fn_rnd(akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest)
-{
-    PREPARE_ERROR(errctx);
-    akbasic_Value *arg = NULL;
-    akbasic_Value *out = NULL;
-    const int64_t modulus = 2147483648;
-
-    (void)lval; (void)rval;
-    PASS(errctx, first_arg(obj, expr, "RND", NULL, &arg, &out));
-    FAIL_NONZERO_RETURN(errctx, (arg->valuetype != AKBASIC_TYPE_INTEGER), AKBASIC_ERR_TYPE,
-			"RND expected an integer");
-    FAIL_ZERO_RETURN(errctx, (arg->intval > 0), AKBASIC_ERR_VALUE,
-		     "RND count %" PRId64 " must be positive", arg->intval);
-
-    if ( !obj->rndseeded ) {
-	obj->rndseed = obj->timems % modulus;
-	obj->rndseeded = true;
-    }
-    obj->rndseed = (obj->rndseed * 1103515245 + 12345) % modulus;
-    out->valuetype = AKBASIC_TYPE_INTEGER;
-    out->intval = (obj->rndseed / 65536) % arg->intval;
-    *dest = out;
-    SUCCEED_RETURN(errctx);
-}
-
 akerr_ErrorContext *akbasic_fn_hex(akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest)
 {
     PREPARE_ERROR(errctx);

src/verbs.c

@@ -37,7 +37,6 @@ static const akbasic_Verb VERBS[] = {
     { "ABS",          AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_abs },
     { "AND",          AKBASIC_TOK_AND,                  -1, NULL,                  NULL },
     { "APPEND",       AKBASIC_TOK_COMMAND,              -1, akbasic_parse_arglist, akbasic_cmd_append },
-    { "ASC",          AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_asc },
     { "ATN",          AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_atn },
     { "AUTO",         AKBASIC_TOK_COMMAND_IMMEDIATE,    -1, NULL,                  akbasic_cmd_auto },
     { "BACKUP",       AKBASIC_TOK_COMMAND,              -1, akbasic_parse_optional_arglist, akbasic_cmd_backup },
@@ -147,7 +146,6 @@ static const akbasic_Verb VERBS[] = {
     { "RGR",          AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_rgr },
     { "RIGHT",        AKBASIC_TOK_FUNCTION,              2, NULL,                  akbasic_fn_right },
     { "RMENU",        AKBASIC_TOK_FUNCTION,              2, NULL,                  akbasic_fn_rmenu },
-    { "RND",          AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_rnd },
     { "RSPCOLOR",     AKBASIC_TOK_FUNCTION,              1, NULL,                  akbasic_fn_rspcolor },
     { "RSPHIT",       AKBASIC_TOK_FUNCTION,              2, NULL,                  akbasic_fn_rsphit },
     { "RSPPOS",       AKBASIC_TOK_FUNCTION,              2, NULL,                  akbasic_fn_rsppos },

src/verbs.h

@@ -140,7 +140,6 @@ akerr_ErrorContext AKERR_NOIGNORE *akbasic_cmd_stop(struct akbasic_Runtime *obj,
 
 /* Function handlers -- src/runtime_functions.c */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_abs(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
-akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_asc(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_atn(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_chr(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_cos(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
@@ -155,7 +154,6 @@ akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_peek(struct akbasic_Runtime *obj,
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_pointer(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_pointervar(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_rad(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
-akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_rnd(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_right(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_sgn(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_fn_shl(struct akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest);

tests/for_semantics.c

@@ -81,7 +81,7 @@ static void test_counter_survives_the_loop(void)
  * `FOR I = 1 TO 1` executes the body one time on every BASIC there has ever
  * been. Here the entry test treats "the counter has reached the limit" as
  * "do not enter", so the body is skipped entirely -- and
- * tests/reference/language/flowcontrol/forloopwaitingforcommand.bas pins that,
+ * tests/language/flowcontrol/forloopwaitingforcommand.bas pins that,
  * which is why this cannot simply be corrected.
  */
 static void test_single_iteration_loop(void)

tests/language/README.md

@@ -0,0 +1,16 @@
+# The language test corpus
+
+The `.bas` files in this directory and their sibling `.txt` files are the editable language
+corpus. CMake registers every program as an individual `local_*` CTest case and compares its
+output with the sibling expectation.
+
+The corpus includes cases carried over from the deprecated Go implementation as well as cases
+written for this interpreter. Their provenance is useful when investigating a regression, but it
+does not make any case immutable or turn the old implementation into a specification.
+
+**Change a program and its expectation deliberately and in the same commit.** If the changed
+output represents an intentional language decision, record the reason in `TODO.md` or the
+relevant documentation. If it is an accidental change, fix the interpreter instead.
+
+The `examples/` subdirectory contains complete BASIC programs used as worked examples. It is
+part of the same corpus and follows the same `.bas`/`.txt` pairing rule.

tests/language/functions/asc.bas

@@ -1,3 +0,0 @@
-10 PRINT "97 : " + ASC("a")
-20 PRINT "65 : " + ASC("A")
-30 PRINT "64 : " + ASC("@")

tests/language/functions/asc.txt

@@ -1,3 +0,0 @@
-97 : 97
-65 : 65
-64 : 64