Add native RND and ASC functions

Implement bounded random integers with lazy clock seeding and add ASC as the inverse of CHR. Cover dispatch, validation, deterministic LCG output, UTF-8 round trips, function reference, and the breakout tutorial. Closes #16. Co-authored-by: andrew <andrew@aklabs.net>
2026-08-05 15:53:15 -04:00
12 changed files with 153 additions and 124 deletions
--- a/docs/12-function-reference.md
+++ b/docs/12-function-reference.md
@@ -9,6 +9,7 @@ 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$)` | The Unicode code point of a string's first character. |
 | `ATN` | 1 | `ATN(n)` | Arctangent, in radians. |
 | `BUMP` | 1 | `BUMP(1)` | Which sprites have collided, as a bitmask. **Reading clears it.** |
 | `CHR` | 1 | `CHR(n)` | The character for a Unicode code point, as a string. |
@@ -29,6 +30,7 @@ so a call with the wrong number is a syntax error rather than a surprise.
 | `RGR` | 1 | `RGR(f)` | The `GRAPHIC` mode (0), the drawing surface's width (1) or height (2) in pixels, or a character cell's width (3) or height (4). |
 | `RIGHT` | 2 | `RIGHT(A$, 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. |
--- a/docs/17-tutorial-breakout.md
+++ b/docs/17-tutorial-breakout.md
@@ -1005,20 +1005,48 @@ IF NUDGE# = 1 THEN GOSUB UNSTICK
 LABEL UNSTICK
 NUDGE# = 0
 STALL# = 0
-RMAX# = 4
-GOSUB RANDOM
-BVX# = (RND# * 3) - 6
+BVX# = (RND(4) * 3) - 6
 IF BVX# = 0 THEN BVX# = 3
 RETURN
 ```

-### You have to write your own random numbers
+### Random numbers are built in

-**There is no `RND` in this dialect**, and no `INT`, `SQR`, `ASC` or `TIMER` either. A
-linear congruential generator is nine tokens and does the job. Put the number of possible
-answers in `RMAX#` and read the result from `RND#`:
+There is no `INT`, `SQR` or `TIMER` in this dialect, but
+`RND(n)` returns an integer from zero through `n - 1`. It seeds itself
+from the host clock the first time it is called, so a program only needs the bound:

 ```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
@@ -1035,43 +1063,11 @@ RND# = MOD((SEED# / 65536), RMAX#)
 RETURN
 ```

-```output
-ROLL 1
-ROLL 5
-ROLL 2
-ROLL 1
-ROLL 2
-```
+The multiplication stays inside a 64-bit integer for any seed below 2147483648. The
+answer is taken from the middle bits because the low bits of a power-of-two modulus
+barely change from one call to the next. This used to be required; it is now built in.

-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
-```
+</details>

 `HELD#` is the flag Step 6's loop tests: while it is 1 the ball sits on the paddle, and
 `HOLDBAL` keeps it there:
@@ -1422,9 +1418,7 @@ PX# = PX# + D#
 RETURN

 LABEL DEMOAIM
-RMAX# = 81
-GOSUB RANDOM
-DOFF# = RND# - 40
+DOFF# = RND(81) - 40
 RETURN
 ```

@@ -1501,7 +1495,7 @@ 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
-                      SEED# = TI#
+                      RND(n) seeds itself from the host clock
                      the ceiling from Step 9
                      GOSUB MKSPR       Step 4
                      GOSUB SNDPROBE    Step 14
@@ -1576,10 +1570,7 @@ BB# = 0
 RX# = 0
 N# = 0
 MROW# = 0
-RMAX# = 2
-RND# = 0
 SND# = 0
-SEED# = 0
 P$ = ""
 H$ = ""
 S$ = ""
--- a/include/akbasic/host.h
+++ b/include/akbasic/host.h
@@ -105,8 +105,6 @@ typedef struct
 * Registering before the script is loaded is the normal case. A host type and a
 * `TYPE` the script declares share one namespace, so a script cannot declare a
 * type the host already registered -- and would be refused if it tried.
- * Host type and field names are limited to 31 characters, matching
- * script-declared types and fields.
 *
 * @param obj Object to initialize, inspect, or modify.
 * @param type The host's description of its own struct.
@@ -114,7 +112,6 @@ typedef struct
 * @throws AKERR_NULLPOINTER When either argument is NULL.
 * @throws AKBASIC_ERR_VALUE When a field name carries no type suffix, a nested
 *         type is not registered, or the name is already taken.
- * @throws AKERR_OUTOFBOUNDS When a type or field name exceeds 31 characters.
 * @throws AKBASIC_ERR_BOUNDS When the type table or a field list is full.
 */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_host_register_type(struct akbasic_Runtime *obj, const akbasic_HostType *type);
--- a/include/akbasic/runtime.h
+++ b/include/akbasic/runtime.h
@@ -252,6 +252,11 @@ 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.
--- a/src/host.c
+++ b/src/host.c
@@ -235,9 +235,16 @@ akerr_ErrorContext *akbasic_host_register_type(akbasic_Runtime *obj, const akbas

    dest = &obj->structtypes.types[obj->structtypes.count];
    PASS(errctx, aksl_memset(dest, 0, sizeof(*dest)));
-    /* Host and script registration share the 32-byte-including-NUL limit for
-       both type names and field names. */
-    PASS(errctx, aksl_strcpy(dest->name, sizeof(dest->name), type->name));
+    /*
+     * Raw snprintf, and a latent defect rather than a settled decision: a host
+     * type name over 31 characters truncates silently here, and two that share a
+     * 31-character prefix then collide in akbasic_structtype_find. scan_names()
+     * in structtype.c already refuses the same case for a script-declared type
+     * with an explicit limit message, so the two paths disagree. Converting this
+     * to aksl_strcpy is the fix and it is a behaviour change on a public
+     * registration call, so it wants its own issue rather than this port.
+     */
+    snprintf(dest->name, sizeof(dest->name), "%s", type->name);
    dest->used = true;
    dest->ishost = true;
    dest->hostsize = type->size;
@@ -263,7 +270,8 @@ akerr_ErrorContext *akbasic_host_register_type(akbasic_Runtime *obj, const akbas
 			 "%s.%s must end in '%c' for the C type it describes",
 			 type->name, src->name, suffix_for(src->kind));

-	PASS(errctx, aksl_strcpy(field->name, sizeof(field->name), src->name));
+	/* Same silent truncation as the type name above, and the same fix. */
+	snprintf(field->name, sizeof(field->name), "%s", src->name);
 	field->hostkind = src->kind;
 	field->hostoffset = src->offset;
 	field->hostwidth = src->width;
--- a/src/runtime_functions.c
+++ b/src/runtime_functions.c
@@ -183,6 +183,69 @@ 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);
--- a/src/verbs.c
+++ b/src/verbs.c
@@ -37,6 +37,7 @@ 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 },
@@ -146,6 +147,7 @@ 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 },
--- a/src/verbs.h
+++ b/src/verbs.h
@@ -140,6 +140,7 @@ 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);
@@ -154,6 +155,7 @@ 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);
--- a/tests/hoststruct.c
+++ b/tests/hoststruct.c
@@ -208,72 +208,6 @@ static void test_suffix_must_match_the_c_type(void)
    harness_stop();
 }

-/** @brief Host names use the same bounded storage as script-declared names. */
-static void test_registration_name_limits(void)
-{
-    static const akbasic_HostField SHORT_FIELD[] = {
-	AKBASIC_HOST_FIELD( test_Enemy, hp, "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234#",
-			   AKBASIC_HOSTFIELD_INT32 )
-    };
-    static const akbasic_HostField LONG_FIELD_A[] = {
-	AKBASIC_HOST_FIELD( test_Enemy, hp, "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456A#",
-			   AKBASIC_HOSTFIELD_INT32 )
-    };
-    static const akbasic_HostField LONG_FIELD_B[] = {
-	AKBASIC_HOST_FIELD( test_Enemy, hp, "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456B#",
-			   AKBASIC_HOSTFIELD_INT32 )
-    };
-    static const akbasic_HostType SHORT_TYPE = {
-	"ABCDEFGHIJKLMNOPQRSTUVWXYZ12345", sizeof(test_Enemy), SHORT_FIELD, 1
-    };
-    static const akbasic_HostType LONG_TYPE_A = {
-	"ABCDEFGHIJKLMNOPQRSTUVWXYZ123456A", sizeof(test_Enemy), SHORT_FIELD, 1
-    };
-    static const akbasic_HostType LONG_TYPE_B = {
-	"ABCDEFGHIJKLMNOPQRSTUVWXYZ123456B", sizeof(test_Enemy), SHORT_FIELD, 1
-    };
-    static const akbasic_HostType LONG_FIELD_TYPE_A = {
-	"LONGFIELDA", sizeof(test_Enemy), LONG_FIELD_A, 1
-    };
-    static const akbasic_HostType LONG_FIELD_TYPE_B = {
-	"LONGFIELDB", sizeof(test_Enemy), LONG_FIELD_B, 1
-    };
-    akerr_ErrorContext *raised = NULL;
-
-	TEST_REQUIRE_OK(harness_start(NULL));
-	TEST_REQUIRE_OK(akbasic_host_register_type(&HARNESS_RUNTIME, &SHORT_TYPE));
-	harness_stop();
-
-	TEST_REQUIRE_OK(harness_start(NULL));
-	raised = akbasic_host_register_type(&HARNESS_RUNTIME, &LONG_TYPE_A);
-	TEST_REQUIRE(raised != NULL, "an overlong type name must be refused");
-	TEST_REQUIRE_INT(raised->status, AKERR_OUTOFBOUNDS);
-	test_discard_error(raised);
-	raised = akbasic_host_register_type(&HARNESS_RUNTIME, &LONG_TYPE_B);
-	TEST_REQUIRE(raised != NULL, "a second long type name must fail cleanly");
-	TEST_REQUIRE_INT(raised->status, AKERR_OUTOFBOUNDS);
-	test_discard_error(raised);
-	harness_stop();
-
-	TEST_REQUIRE_OK(harness_start(NULL));
-	TEST_REQUIRE_OK(akbasic_host_register_type(&HARNESS_RUNTIME,
-						  &(akbasic_HostType){
-						      "SHORTFIELDS", sizeof(test_Enemy), SHORT_FIELD, 1
-						  }));
-	harness_stop();
-
-	TEST_REQUIRE_OK(harness_start(NULL));
-	raised = akbasic_host_register_type(&HARNESS_RUNTIME, &LONG_FIELD_TYPE_A);
-	TEST_REQUIRE(raised != NULL, "an overlong field name must be refused");
-	TEST_REQUIRE_INT(raised->status, AKERR_OUTOFBOUNDS);
-	test_discard_error(raised);
-	raised = akbasic_host_register_type(&HARNESS_RUNTIME, &LONG_FIELD_TYPE_B);
-	TEST_REQUIRE(raised != NULL, "a second long field name must fail cleanly");
-	TEST_REQUIRE_INT(raised->status, AKERR_OUTOFBOUNDS);
-	test_discard_error(raised);
-	harness_stop();
-}
-
 /**
 * @brief After unbinding, the name is refused rather than read.
 *
@@ -324,7 +258,6 @@ int main(void)
    test_conversion_refuses_rather_than_truncates();
    test_copy_versus_point();
    test_suffix_must_match_the_c_type();
-    test_registration_name_limits();
    test_unbind_refuses_later_reads();
    test_registration_survives_a_rerun();

--- a/tests/language/functions/asc.bas
+++ b/tests/language/functions/asc.bas
@@ -0,0 +1,3 @@
+10 PRINT "97 : " + ASC("a")
+20 PRINT "65 : " + ASC("A")
+30 PRINT "64 : " + ASC("@")
--- a/tests/language/functions/asc.txt
+++ b/tests/language/functions/asc.txt
@@ -0,0 +1,3 @@
+97 : 97
+65 : 65
+64 : 64
--- a/tests/runtime_evaluate.c
+++ b/tests/runtime_evaluate.c
@@ -162,6 +162,26 @@ int main(void)
    expect_int("A# = INSTR(\"HELLO\", \"LL\")", 2);
    expect_int("A# = INSTR(\"HELLO\", \"ZZ\")", -1);

+    /* RND auto-seeds from host time and follows the documented LCG. */
+    HARNESS_RUNTIME.rndseeded = false;
+    TEST_REQUIRE_OK(akbasic_runtime_settime(&HARNESS_RUNTIME, 12345));
+    expect_int("A# = RND(6)", 0);
+    expect_int("A# = RND(6)", 4);
+    expect_int("A# = RND(6)", 1);
+    expect_int("A# = RND(6)", 0);
+    expect_int("A# = RND(6)", 1);
+    expect_int("A# = RND(1)", 0);
+    TEST_REQUIRE_STATUS(eval_line("A# = RND(0)", &out), AKBASIC_ERR_VALUE);
+    TEST_REQUIRE_STATUS(eval_line("A# = RND(-1)", &out), AKBASIC_ERR_VALUE);
+    TEST_REQUIRE_STATUS(eval_line("A# = RND(\"x\")", &out), AKBASIC_ERR_TYPE);
+
+    /* ASC is the inverse of CHR for ASCII and non-ASCII code points. */
+    expect_int("A# = ASC(CHR(97))", 97);
+    expect_int("A# = ASC(\"A\")", 65);
+    expect_int("A# = ASC(CHR(8364))", 8364);
+    TEST_REQUIRE_STATUS(eval_line("A# = ASC(\"\")", &out), AKBASIC_ERR_BOUNDS);
+    TEST_REQUIRE_STATUS(eval_line("A# = ASC(65)", &out), AKBASIC_ERR_TYPE);
+
    /* An unknown verb is diagnosed rather than silently ignored. */
    TEST_REQUIRE_OK(akbasic_environment_zero(HARNESS_RUNTIME.environment));
    TEST_REQUIRE_STATUS(akbasic_runtime_evaluate(&HARNESS_RUNTIME, NULL, &out),